: an object that is attached to a wall and used to support or hold up something (such as a shelf)
: a category that includes a certain range of incomes, ages, etc.
: either one of a pair of marks [ ] or 〈 〉 used to enclose words or mathematical symbols
: to place (words, symbols, etc.) within brackets
: to be located at each side of (something)
: to put (two or more people or things) into the same category, group, etc.
What made you want to look up bracket? Please tell us where you read or heard it (including the quote, if possible).