Definition of brackets:
(n) :
A fixture attached to a wall to hold up a shelf.
(n) :
(engineering) Any intermediate object that connects a smaller part to a larger part, the smaller part typically projecting sideways from the larger part.
(n) :
(nautical) A short crooked timber, resembling a knee, used as a support.
(n) :
(military) The cheek or side of an ordnance carriage, supporting the trunnions.
(n) :
Any of the characters “(”, “)”, “[”, “]”, “{”, “}”, “⟨”, “⟩”, “<”, “>”, or the like, used in pairs to enclose parenthetic remarks, sections of mathematical expressions, etc.
(n) :
(UK) “(” and “)” specifically, the other forms above requiring adjectives for disambiguation.