The Collaborative International Dictionary of English v.0.48:

Pressure \Pres"sure\ (?; 138), n. [OF., fr. L. pressura, fr.
   premere. See 4th Press.]
   1. The act of pressing, or the condition of being pressed;
      compression; a squeezing; a crushing; as, a pressure of
      the hand.
      [1913 Webster]

   2. A contrasting force or impulse of any kind; as, the
      pressure of poverty; the pressure of taxes; the pressure
      of motives on the mind; the pressure of civilization.
      [1913 Webster]

            Where the pressure of danger was not felt.
                                                  --Macaulay.
      [1913 Webster]

   3. Affliction; distress; grievance.
      [1913 Webster]

            My people's pressures are grievous.   --Eikon
                                                  Basilike.
      [1913 Webster]

            In the midst of his great troubles and pressures.
                                                  --Atterbury.
      [1913 Webster]

   4. Urgency; as, the pressure of business.
      [1913 Webster]

   5. Impression; stamp; character impressed.
      [1913 Webster]

            All saws of books, all forms, all pressures past.
                                                  --Shak.
      [1913 Webster]

   6. (Mech.) The action of a force against some obstacle or
      opposing force; a force in the nature of a thrust,
      distributed over a surface, often estimated with reference
      to the amount upon a unit's area.
      [1913 Webster]

   7. Electro-motive force.
      [Webster 1913 Suppl.]

   Atmospheric pressure, Center of pressure, etc. See under
      Atmospheric, Center, etc.

   Back pressure (Steam engine), pressure which resists the
      motion of the piston, as the pressure of exhaust steam
      which does not find free outlet.

   Fluid pressure, pressure like that exerted by a fluid. It
      is a thrust which is normal and equally intense in all
      directions around a point. --Rankine.

   Pressure gauge, a gauge for indicating fluid pressure; a
      manometer.
      [1913 Webster]

WordNet (r) 3.0 (2006):

pressure
    n 1: the force applied to a unit area of surface; measured in
         pascals (SI unit) or in dynes (cgs unit); "the compressed
         gas exerts an increased pressure" [syn: pressure,
         pressure level, force per unit area]
    2: a force that compels; "the public brought pressure to bear on
       the government"
    3: the act of pressing; the exertion of pressure; "he gave the
       button a press"; "he used pressure to stop the bleeding"; "at
       the pressing of a button" [syn: press, pressure,
       pressing]
    4: the state of demanding notice or attention; "the insistence
       of their hunger"; "the press of business matters" [syn:
       imperativeness, insistence, insistency, press,
       pressure]
    5: the somatic sensation that results from applying force to an
       area of skin; "the sensitivity of his skin to pressure and
       temperature was normal" [syn: pressure, pressure
       sensation]
    6: an oppressive condition of physical or mental or social or
       economic distress
    7: the pressure exerted by the atmosphere [syn: atmospheric
       pressure, air pressure, pressure]
    v 1: to cause to do through pressure or necessity, by physical,
         moral or intellectual means :"She forced him to take a job
         in the city"; "He squeezed her for information" [syn:
         coerce, hale, squeeze, pressure, force]
    2: exert pressure on someone through threats [syn: blackmail,
       blackjack, pressure]

Moby Thesaurus II by Grady Ward, 1.0:

297 Moby Thesaurus words for "pressure":
   abetment, adverse circumstances, adversity, advocate, affliction,
   aggravation, albatross, annoyance, apply pressure,
   argumentum baculinum, ascendancy, authority, bale, bear against,
   bear down on, bear down upon, bear hard upon, bearing, beset,
   besiege, blandish, blandishment, blight, boost, bug, bummer, bump,
   bunt, burden, burdening, burthen, butt, buttonhole, buttonholing,
   cajole, cajolement, cajolery, call on, call upon, care, caressing,
   cargo, case of need, charge, charging, charisma, charm, clamping,
   clamping down, clout, clutch, coax, coaxing, coerce, coercion,
   compel, compression, compulsion, consequence, constrain,
   constraint, constraints, control, credit, crisis, cross, crunch,
   crush, crushing, cumber, cumbrance, curse, deadweight, demand,
   demandingness, demands, difficulties, difficulty, dig,
   dire necessity, distress, dominance, domination, downer, drag,
   drive, dun, dunning, duress, effect, emergency, eminence,
   enchantment, encouragement, encumbrance, esteem, exert pressure,
   exhort, exigence, exigencies, exigency, favor, feeling, fingering,
   force, freight, friction, frottage, goading, good feeling,
   greatness, handicap, handling, hard knocks, hard life, hard lot,
   hardcase, hardship, head, high pressure, high-pressure, hold,
   hustle, immediacy, impel, imperative, imperativeness, importance,
   importunacy, importunateness, importune, importunity, impulse,
   impulsion, incidental power, incubus, incumbency, inducement,
   influence, influentiality, influentialness, insinuation, insist,
   insist on, insist upon, insistence, instance, intimidate,
   intimidation, irritation, jab, jawbone, jog, joggle, jolt, jostle,
   lading, leadership, lean on, leverage, load, loading, lobby,
   magnetism, make, manipulation, mastery, matter of necessity,
   mental strain, millstone, moment, nag, nag at, nagging, needling,
   nervous strain, nervous tension, nip, nudge, oppression, overload,
   overtaxing, overweighting, palpation, persistence, personality,
   persuade, persuasion, pertinaciousness, pertinacity, pester,
   pestering, petting, pinch, plague, plaguing, plead with, plight,
   ply, plying, poke, potency, power, precedence, predicament,
   predominance, preponderance, press, pressing, pressingness,
   prestige, prevail on, prevail upon, pricking, priority, problems,
   prod, prodding, prominence, punch, purchase, push, put pressure on,
   rank, rash impulse, recommend, reign, repute, require, rigor,
   rubbing, rule, rush, saddling, say, sea of troubles, seniority,
   shove, soft-soap, spurring, squeeze, squeezing, stature, strain,
   straits, strength, stress, stress and strain, stress of life,
   stroking, strong-arm tactics, suasion, subtle influence,
   suggestion, superincumbency, supremacy, surcharge, sway,
   sweet-talk, tautness, taxing, tease, teasing, tenseness, tension,
   the big stick, the bludgeon, the club, the jackboot,
   the mailed fist, the strong arm, the sword, thrust, tightening,
   torque, torsion, touching, trial, tribulation, trouble, troubles,
   tweak, upper hand, urge, urgency, urgent need, urging,
   vale of tears, vexation, vicissitude, violence, weight,
   weightiness, wheedle, wheedling, whip hand, work on