Brackets

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).
Informal. an 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.
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.
Contemporary Examples

It’s Time to Rip the Money Out of the NCAA Robert Silverman March 31, 2014
Michael Tomasky on Mitt Romney’s Tax-Plan Flim-Flam Michael Tomasky February 24, 2012
A Method to March Madness Ben Teitelbaum March 19, 2013
Pat O’Brien Breaks Down the NCAA Tournament Pat O’Brien March 15, 2009
A History of Budget Projections in 13 Charts Megan McArdle February 4, 2013

Historical Examples

The International Monthly, Volume 3, No. 4, July, 1851 Various
Chronicles of Border Warfare Alexander Scott Withers
Water Supply: the Present Practice of Sinking and Boring Wells Ernest Spon
On Laboratory Arts Richard Threlfall
The Long Roll Mary Johnston

noun
an L-shaped or other support fixed to a wall to hold a shelf, etc
one or more wall shelves carried on brackets
(architect) a support projecting from the side of a wall or other structure See also corbel, ancon, console2
Also called square bracket. either of a pair of characters, [ ], used to enclose a section of writing or printing to separate it from the main text
a general name for parenthesis, square bracket, brace (sense 6)
a group or category falling within or between certain defined limits: the lower income bracket
the distance between two preliminary shots of artillery fire in range-finding
a skating figure consisting of two arcs meeting at a point, tracing the shape ⋎
verb (transitive) -kets, -keting, -keted
to fix or support by means of a bracket or brackets
to put (written or printed matter) in brackets, esp as being irrelevant, spurious, or bearing a separate relationship of some kind to the rest of the text
to couple or join (two lines of text, etc) with a brace
(often foll by with) to group or class together: to bracket Marx with the philosophers
to adjust (artillery fire) until the target is hit
n.
v.