The Collaborative International Dictionary of English v.0.48:

Firm \Firm\, n. [It. firma the (firm, sure, or confirming)
   signature or subscription, or Pg. firma signature, firm, cf.
   Sp. firma signature; all fr. L. firmus, adj., firm. See
   Firm, a.]
   The name, title, or style, under which a company transacts
   business; a partnership of two or more persons; a commercial
   house; as, the firm of Hope & Co.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Firm \Firm\, v. t. [OE. fermen to make firm, F. fermer, fr. L.
   firmare to make firm. See Firm, a.]
   1. To fix; to settle; to confirm; to establish. [Obs.]
      [1913 Webster]

            And Jove has firmed it with an awful nod. --Dryden.
      [1913 Webster]

   2. To fix or direct with firmness. [Obs.]
      [1913 Webster]

            He on his card and compass firms his eye. --Spenser.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Firm \Firm\, a. [Compar. Firmer; superl. Firmest.] [OE.
   ferme, F. ferme, fr.L. firmus; cf. Skr. dharman support, law,
   order, dh? to hold fast, carry. Cf. Farm, Throne.]
   1. Fixed; hence, closely compressed; compact; substantial;
      hard; solid; -- applied to the matter of bodies; as, firm
      flesh; firm muscles, firm wood.
      [1913 Webster]

   2. Not easily excited or disturbed; unchanging in purpose;
      fixed; steady; constant; stable; unshaken; not easily
      changed in feelings or will; strong; as, a firm believer;
      a firm friend; a firm adherent.
      [1913 Webster]

            Under spread ensigns, moving nigh, in slow
            But firm battalion.                   --Milton.
      [1913 Webster]

            By one man's firm obediency fully tried. --Milton.
      [1913 Webster]

   3. Solid; -- opposed to fluid; as, firm land.
      [1913 Webster]

   4. Indicating firmness; as, a firm tread; a firm countenance.

   Syn: Compact; dense; hard; solid; stanch; robust; strong;
        sturdly; fixed; steady; resolute; constant.
        [1913 Webster]

WordNet (r) 3.0 (2006):

firm
    adv 1: with resolute determination; "we firmly believed it";
           "you must stand firm" [syn: firm, firmly,
           steadfastly, unwaveringly]
    adj 1: marked by firm determination or resolution; not shakable;
           "firm convictions"; "a firm mouth"; "steadfast resolve";
           "a man of unbendable perseverence"; "unwavering loyalty"
           [syn: firm, steadfast, steady, stiff,
           unbendable, unfaltering, unshakable, unwavering]
    2: not soft or yielding to pressure; "a firm mattress"; "the
       snow was firm underfoot"; "solid ground" [syn: firm,
       solid]
    3: strong and sure; "a firm grasp"; "gave a strong pull on the
       rope" [syn: firm, strong]
    4: not subject to revision or change; "a firm contract"; "a firm
       offer"
    5: (of especially a person's physical features) not shaking or
       trembling; "his voice was firm and confident"; "a firm step"
    6: not liable to fluctuate or especially to fall; "stocks are
       still firm" [syn: firm, steady, unfluctuating]
    7: securely established; "holds a firm position as the country's
       leading poet"
    8: possessing the tone and resiliency of healthy tissue; "firm
       muscles"
    9: securely fixed in place; "the post was still firm after being
       hit by the car" [syn: fast, firm, immobile]
    10: unwavering in devotion to friend or vow or cause; "a firm
        ally"; "loyal supporters"; "the true-hearted soldier...of
        Tippecanoe"- Campaign song for William Henry Harrison; "fast
        friends" [syn: firm, loyal, truehearted, fast(a)]
    n 1: the members of a business organization that owns or
         operates one or more establishments; "he worked for a
         brokerage house" [syn: firm, house, business firm]
    v 1: become taut or tauter; "Your muscles will firm when you
         exercise regularly"; "the rope tautened" [syn: tauten,
         firm]
    2: make taut or tauter; "tauten a rope" [syn: tauten, firm]

Moby Thesaurus II by Grady Ward, 1.0:

405 Moby Thesaurus words for "firm":
   Aktiengesellschaft, CIA, Central Intelligence Agency, Christian,
   abiding, accepted, adamant, adamantine, agency, airtight,
   aktiebolag, anchored, anneal, approved, at a standstill, atelier,
   authentic, authoritative, balance, balanced, ballast, barbershop,
   beauty parlor, beauty shop, bench, body corporate, bonded,
   bristling, bulky, business, business establishment, butcher shop,
   calcify, calculable, callous, canonical, cartel, case harden,
   cast-iron, cemented, certain, chamber of commerce, changeless,
   close, close-knit, close-textured, close-woven, combine,
   commercial enterprise, compact, compacted, compagnie, company,
   compressed, concentrated, concern, concrete, condensed, congested,
   conglomerate, conglomerate corporation, consistent, consolidate,
   consolidated, consolidating company, consortium, constant,
   continuing, conventional, cool, copartnership, cornify,
   corporate body, corporation, correct, counterbalance, crammed,
   crammed full, crawling, crowded, customary, decided, decisive,
   definite, dense, dependable, desk, determine, determined, devoted,
   diversified corporation, dogged, dour, durable, dustproof,
   dusttight, enduring, enterprise, establish, established,
   establishment, evangelical, exact, explicit, facility, fail-safe,
   faithful, faithworthy, fast, fastened, fiducial, firm as Gibraltar,
   firm up, firmly, fixed, fixedly, flat, flinty, fossilize, freeze,
   frozen, full, fundamentalist, gasproof, gastight, glued, gluey,
   going, grim, guaranteed, hard, hard-core, harden, harmless, heavy,
   hermetic, hermetically sealed, hidebound, hold, holding company,
   house, immobile, immobilize, immotile, immotive, immovable,
   immutable, impenetrable, impermeable, imperturbable, implacable,
   impliable, in equilibrium, indurate, industry, inelastic,
   inexorable, inflexible, infrangible, installation, institution,
   intact, intransigent, invincible, inviolate, invulnerable, iron,
   ironbound, ironclad, ironhanded, irreconcilable, irremovable,
   jam-packed, jammed, joint-stock association, joint-stock company,
   keep, lapidify, lasting, lightproof, lighttight, literal, lithify,
   loft, loyal, made of iron, marble-constant, massive, moored,
   muscle-bound, nail down, never-failing, nonporous, obdurate,
   obstinate, of the faith, oilproof, oiltight, operating company,
   organization, orthodox, orthodoxical, ossify, outfit, packed,
   parlor, partnership, pat, permanent, perpetual, persistent,
   petrify, pin down, plunderbund, pokerlike, pool, populous,
   positive, predictable, prevailing, procrustean, proper,
   proprietorship, public utility, purist, puristic, puritan,
   puritanic, quiescent, rainproof, raintight, ramrodlike, received,
   relentless, reliable, remaining, renitent, resolute, resolve,
   resolved, retain, right, rigid, rigorist, rigoristic, rigorous,
   riskless, rock-ribbed, rockbound, rodlike, rugged, scriptural,
   sealed, secure, serried, set, set on, set up, set upon,
   settle down, settled, shop, shut fast, smokeproof, smoketight,
   snug, solid, solidify, solidly, sot, sound, specific, stabilitate,
   stabilize, stable, standard, standpat, starched, starchy, stated,
   static, stationary, staunch, staying, steadfast, steadfastly,
   steady, steel, steely, stern, stick, stiff, stiff as buckram,
   stipulated, stock company, stormproof, stormtight, stout,
   straightlaced, straitlaced, strict, strong, stubborn, stuck,
   studio, sturdy, substantial, sure, surefire, sustained, swarming,
   sweatshop, syndicate, taped, taut, teeming, temper, tenacious,
   tense, textual, thick, thick-growing, thickset, tight, tightly,
   torpid, tough, toughen, trade association, traditional,
   traditionalistic, transfix, true, true-blue, trust, trustworthy,
   trusty, unaffected, unalterable, unaltered, unbending, unbreakable,
   unchangeable, unchanged, unchanging, unchecked, uncompromising,
   undangerous, undeflectable, undestroyed, undeviating, unfading,
   unfailing, unfaltering, unflappable, unflinching, ungiving,
   unhazardous, unmovable, unmoved, unmoving, unperilous,
   unprecarious, unqualified, unrelaxed, unrelenting, unrisky,
   unshakable, unshakeable, unshaken, unshifting, unswerving,
   unvaried, unvarying, unwavering, unyielding, utility, virgate,
   viscid, viscose, viscous, vitrify, warranteed, water-repellant,
   waterproof, watertight, wedged, well-balanced, well-built,
   well-constructed, well-founded, well-grounded, well-made,
   windproof, windtight, without nerves, work site, work space,
   workbench, workhouse, working space, workplace, workroom, workshop,
   worktable



Bouvier's Law Dictionary, Revised 6th Ed (1856):

FIRM. The persons composing a partnership, taken collectively, are called
the firm. Sometimes this word is used synonymously with partnership.
     2. The name of a firm should be distinct from the names of all other
firms. When there is a confusion in this respect, the partners composing one
firm May, in some cases, be made responsible for the debts of another. For
example, where three persons carried on a trade under the firm of King and
Company, and two of those persons, with another, under the same firm,
carried on another partnership; a bill under the firm, and which was drawn
on account of the one partnership, was made the ground of an action of
assumpsit against the other. Lord Kenyon was of opinion that this company
was liable; that the partner not connected with the company that drew the
bill, having traded along with the other partner under that firm, persons
taking bills under it, though without his knowledge, had a right to look to
him for payment. Peake's N. P. Cas. 80; and see 7 East, R. 210; 2 Bell's
Com. 670, 6th ed.; 3 Mart. N. S. 39. But it would seem, 1st. That any act
distinctly indicating credit to be given to one of the partnerships, will
fix the election of the creditor to that company; and 2d. That making a
claim on either of the firms, or, when they are insolvent, on either of the
estates, will have the same effect.
     3. When the style of the firm has been agreed upon, for example, John
Doe and Company, the partners who sign the name of the firm are required to
use such name in the style adopted, and a departure from it may have the
double effect of rendering the individual partner who signs it, personally
liable not only to third persons, but to his co-partners; Story, Partn. Sec.
102, 202 and it will be a breach of the agreement, if the partner sign his
own name, and add, "for himself and partners." Colly. Partn. B. 2, c. 2,
Sec. 2; 2 Jac. & Walk. 266.
     4. As a general rule a firm will be bound by the acts of one of the
partners in the course of their trade and business, and will be discharged
by transactions with a single partner. For example, the payment or
satisfaction of a debt by a partner, is a satisfaction and payment by them
all; and a release to one partner, is in release to them all. Go. Litt. 232
n; 6 T. R. 525. Vide Partner; Partnership.
     5. It not unfrequently happens that the name of the firm is the name of
only one of the partners, and that such partner does business in his own
name on his private or separate account. In such case, if the contract be
entered into for the firm, and there is express or implied proof of that
fact, the partnership will be bound by it; but when there is no such proof,
the presumption will be that the debt was contracted by the partner on his
own separate account, and the firm will not be responsible. Story on Part.
Sec. 139; Colly. on Partn. Book 3, c. 1, Sec. 2; 17 Serg. & Rawle, 165; 5
Mason, 176; 5 Peters, 529; 9 Pick. 274; 2 Bouv. Inst. n. 1442, et seq.