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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