The Collaborative International Dictionary of English v.0.48:

Hard \Hard\ (h[aum]rd), a. [Compar. Harder (-[~e]r); superl.
   Hardest.] [OE. hard, heard, AS. heard; akin to OS. & D.
   hard, G. hart, OHG. herti, harti, Icel. har[eth]r, Dan.
   haard, Sw. h[*a]rd, Goth. hardus, Gr. kraty`s strong,
   ka`rtos, kra`tos, strength, and also to E. -ard, as in
   coward, drunkard, -crat, -cracy in autocrat, democracy; cf.
   Skr. kratu strength, k[.r] to do, make. Cf. Hardy.]
   1. Not easily penetrated, cut, or separated into parts; not
      yielding to pressure; firm; solid; compact; -- applied to
      material bodies, and opposed to soft; as, hard wood;
      hard flesh; a hard apple.
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   2. Difficult, mentally or judicially; not easily apprehended,
      decided, or resolved; as a hard problem.
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            The hard causes they brought unto Moses. --Ex.
                                                  xviii. 26.
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            In which are some things hard to be understood. --2
                                                  Peter iii. 16.
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   3. Difficult to accomplish; full of obstacles; laborious;
      fatiguing; arduous; as, a hard task; a disease hard to
      cure.
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   4. Difficult to resist or control; powerful.
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            The stag was too hard for the horse.  --L'Estrange.
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            A power which will be always too hard for them.
                                                  --Addison.
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   5. Difficult to bear or endure; not easy to put up with or
      consent to; hence, severe; rigorous; oppressive;
      distressing; unjust; grasping; as, a hard lot; hard times;
      hard fare; a hard winter; hard conditions or terms.
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            I never could drive a hard bargain.   --Burke.
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   6. Difficult to please or influence; stern; unyielding;
      obdurate; unsympathetic; unfeeling; cruel; as, a hard
      master; a hard heart; hard words; a hard character.
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   7. Not easy or agreeable to the taste; harsh; stiff; rigid;
      ungraceful; repelling; as, a hard style.
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            Figures harder than even the marble itself.
                                                  --Dryden.
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   8. Rough; acid; sour, as liquors; as, hard cider.
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   9. (Pron.) Abrupt or explosive in utterance; not aspirated,
      sibilated, or pronounced with a gradual change of the
      organs from one position to another; -- said of certain
      consonants, as c in came, and g in go, as distinguished
      from the same letters in center, general, etc.
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   10. Wanting softness or smoothness of utterance; harsh; as, a
       hard tone.
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   11. (Painting)
       (a) Rigid in the drawing or distribution of the figures;
           formal; lacking grace of composition.
       (b) Having disagreeable and abrupt contrasts in the
           coloring or light and shade.
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   Hard cancer, Hard case, etc. See under Cancer, Case,
      etc.

   Hard clam, or Hard-shelled clam (Zool.), the quahog.

   Hard coal, anthracite, as distinguished from bituminous
      coal (soft coal).

   Hard and fast. (Naut.) See under Fast.

   Hard finish (Arch.), a smooth finishing coat of hard fine
      plaster applied to the surface of rough plastering.

   Hard lines, hardship; difficult conditions.

   Hard money, coin or specie, as distinguished from paper
      money.

   Hard oyster (Zool.), the northern native oyster. [Local, U.
      S.]

   Hard pan, the hard stratum of earth lying beneath the soil;
      hence, figuratively, the firm, substantial, fundamental
      part or quality of anything; as, the hard pan of
      character, of a matter in dispute, etc. See Pan.

   Hard rubber. See under Rubber.

   Hard solder. See under Solder.

   Hard water, water, which contains lime or some mineral
      substance rendering it unfit for washing. See Hardness,
      3.

   Hard wood, wood of a solid or hard texture; as walnut, oak,
      ash, box, and the like, in distinction from pine, poplar,
      hemlock, etc.

   In hard condition, in excellent condition for racing;
      having firm muscles; -- said of race horses.

   Syn: Solid; arduous; powerful; trying; unyielding; stubborn;
        stern; flinty; unfeeling; harsh; difficult; severe;
        obdurate; rigid. See Solid, and Arduous.
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The Collaborative International Dictionary of English v.0.48:

Solder \Sol"der\, n. [Formerly soder; F. soudure, OF. soudeure,
   fr. OF. & F. souder to solder, L. solidare to fasten, to make
   solid. See Solid, and cf. Sawder.]
   A metal or metallic alloy used when melted for uniting
   adjacent metallic edges or surfaces; a metallic cement.
   Hence, anything which unites or cements.
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   Hard solder, a solder which fuses only at a red heat, as
      one composed of zinc and copper, or silver and copper,
      etc.

   Soft solder, a solder fusible at comparatively low
      temperatures; as, plumbers' solder, consisting of two
      parts lead and one part tin, is a soft solder.
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WordNet (r) 3.0 (2006):

hard solder
    n 1: solder that contains copper; melts at a relatively high
         temperature; used for brazing