The Collaborative International Dictionary of English v.0.48:

Crotchet \Crotch"et\ (kr?ch"?t; 224), n. [F. crochet, prop., a
   little hook, a dim. from the same source as croc hook. See
   Crook, and cf. Crochet, Crocket, Crosier.]
   1. A forked support; a crotch.
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            The crotchets of their cot in columns rise.
                                                  --Dryden.
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   2. (Mus.) A time note, with a stem, having one fourth the
      value of a semibreve, one half that of a minim, and twice
      that of a quaver; a quarter note.
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   3. (Fort.) An indentation in the glacis of the covered way,
      at a point where a traverse is placed.
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   4. (Mil.) The arrangement of a body of troops, either forward
      or rearward, so as to form a line nearly perpendicular to
      the general line of battle.
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   5. (Print.) A bracket. See Bracket.
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   6. (Med.) An instrument of a hooked form, used in certain
      cases in the extraction of a fetus. --Dunglison.
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   7. A perverse fancy; a whim which takes possession of the
      mind; a conceit.
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            He ruined himself and all that trusted in him by
            crotchets that he could never explain to any
            rational man.                         --De Quincey.
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The Collaborative International Dictionary of English v.0.48:

Crotchet \Crotch"et\, v. i.
   To play music in measured time. [Obs.] --Donne.
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The Collaborative International Dictionary of English v.0.48:

Bracket \Brack"et\, n. [Cf. OF. braguette codpiece, F. brayette,
   Sp. bragueta, also a projecting mold in architecture; dim.
   fr. L. bracae breeches; cf. also, OF. bracon beam, prop,
   support; of unknown origin. Cf. Breeches.]
   [1913 Webster]
   1. (Arch.) An architectural member, plain or ornamental,
      projecting from a wall or pier, to support weight falling
      outside of the same; also, a decorative feature seeming to
      discharge such an office.
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   Note: This is the more general word. See Brace,
         Cantalever, Console, Corbel, Strut.
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   2. (Engin. & Mech.) A piece or combination of pieces, usually
      triangular in general shape, projecting from, or fastened
      to, a wall, or other surface, to support heavy bodies or
      to strengthen angles.
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   3. (Naut.) A shot, crooked timber, resembling a knee, used as
      a support.
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   4. (Mil.) The cheek or side of an ordnance carriage.
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   5. (Print.) One of two characters [], used to inclose a
      reference, explanation, or note, or a part to be excluded
      from a sentence, to indicate an interpolation, to rectify
      a mistake, or to supply an omission, and for certain other
      purposes; -- called also crotchet.
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   6. A gas fixture or lamp holder projecting from the face of a
      wall, column, or the like.
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   7. (Gunnery) A figure determined by firing a projectile
      beyond a target and another short of it, as a basis for
      ascertaining the proper elevation of the piece; -- only
      used in the phrase, to establish a bracket. After the
      bracket is established shots are fired with intermediate
      elevations until the exact range is obtained. In the
      United States navy it is called fork.
      [Webster 1913 Suppl.]

   Bracket light, a gas fixture or a lamp attached to a wall,
      column, etc.
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WordNet (r) 3.0 (2006):

crotchet
    n 1: a sharp curve or crook; a shape resembling a hook [syn:
         hook, crotchet]
    2: a musical note having the time value of a quarter of a whole
       note [syn: quarter note, crotchet]
    3: a strange attitude or habit [syn: oddity, queerness,
       quirk, quirkiness, crotchet]
    4: a small tool or hooklike implement

Moby Thesaurus II by Grady Ward, 1.0:

96 Moby Thesaurus words for "crotchet":
   L, accidental, angle, apex, bee, bend, bifurcation, bight, boutade,
   brainstorm, breve, cant, capriccio, caprice, chevron, coin,
   conceit, corner, crank, craze, crazy idea, crook, deflection,
   demisemiquaver, dogleg, dominant, dominant note, double whole note,
   eccentricity, eighth note, elbow, ell, enharmonic, enharmonic note,
   fad, fancy, fantastic notion, fantasy, flat, flimflam, fool notion,
   fork, freak, freakish inspiration, furcation, half note,
   harebrained idea, hemidemisemiquaver, hook, humor, inflection,
   kink, knee, maggot, megrim, minim, musical note, natural, nook,
   note, notion, passing fancy, patent note, point, quarter note,
   quaver, quirk, quoin, report, responding note, semibreve,
   semiquaver, shaped note, sharp, sixteenth note, sixty-fourth note,
   spiccato, staccato, sustained note, swerve, tercet,
   thirty-second note, tone, toy, triplet, twist, vagary, veer,
   vertex, whim, whim-wham, whimsy, whole note, zag, zig, zigzag