slang Something one particularly prefers, desires, enjoys, or cares about. Often used in negative constructions. Thank you for the invitation, but long-distance cycling just isn't really my bag. I knew classic literature was your bag, so I thought you might like this book I found.
be (not) (one's) bag
slang To be something that one is interested in or enjoys. Usually used in the negative. Dancing just isn't my bag—I always look really foolish. You can tell just by looking at her that fashion design is her bag.