What is Bracket?

Bracket definition and meaning on Dictionary terms:
a support, as of metal or wood, projecting from a wall or the like to hold or bear the weight of a shelf, part of a cornice, etc.
a shelf or shelves so supported.
Also called square bracket. one of two marks [ or ] used in writing or printing to enclose parenthetical matter, interpolations, etc.
Mathematics. brackets,parentheses of various forms indicating that the enclosed quantity is to be treated as a unit.(loosely) vinculum(def 2) expression or formula between a pair of brackets.

a grouping of people based on the amount of their income: the low-income bracket.
a class; grouping; classification: She travels in a different social bracket.
Architecture. any horizontally projecting support for an overhanging weight, as a corbel, cantilever, or console.any of a series of fancifully shaped false consoles beneath an ornamental cornice.

(on a staircase) an ornamental piece filling the angle between a riser and its tread.
Shipbuilding. a flat plate, usually triangular with a flange on one edge, used to unite and reinforce the junction between two flat members or surfaces meeting at an angle.any member for reinforcing the angle between two members or surfaces.

a projecting fixture for gas or electricity.
Gunnery. range or elevation producing both shorts and overs on a target.

verb (used with object)
to furnish with or support by a bracket or brackets.
to place within brackets; couple with a brace.

to associate, mention, or class together: Gossip columnists often bracket them together, so a wedding may be imminent.
Gunnery. to place (shots) both beyond and short of a target.
Photography. to take (additional shots) at exposure levels above and below the estimated correct exposure.