1. [n]  an L-shaped support projecting from a wall (as to hold a shelf)
2. [n]  either of two punctuation marks (< or >) used to enclose textual material
3. [n]  either of two punctuation marks ([ or ]) used to enclose textual material
4. [n]  a category falling within certain defined limits
5. [v]  classify or group
6. [v]  place into brackets; "Please bracket this remark"
7. [v]  support with brackets, as of shelves, for example

1. \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}.]
   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.
   
   Note: This is the more general word. See {Brace},
         {Cantalever}, {Console}, {Corbel}, {Strut}.
   
   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.
   
   3. (Naut.) A shot, crooked timber, resembling a knee, used as
      a support.
   
   4. (Mil.) The cheek or side of an ordnance carriage.
   
   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}.
   
   6. A gas fixture or lamp holder projecting from the face of a
      wall, column, or the like.
   
   {Bracket light}, a gas fixture or a lamp attached to a wall,
      column, etc.
   
   

2. \Brack"et\, v. t. [imp. & p. p. {Bracketed}; p. pr. &
   vb. n. {Bracketing}]
   To place within brackets; to connect by brackets; to furnish
   with brackets.
   
   

3. \Brack"et\, n. (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}.
   
   
   
   

4. \Brack"et\, v. t. (Gunnery)
   To shoot so as to establish a bracket for (an object).
   
   

(Or square bracket) A left bracket or right bracket.

Often used loosely for parentheses, square brackets, braces, angle brackets, or any other kind of unequal paired delimiters.