noun
A vehicle (usually a bus, coach or train) or aircraft with two floors.
A frigate with two decks above the waterline.
(figuratively) Any object with two layers or parts stacked on top of each other.
(journalism) A headline that is two lines long.
(India, LGBTQ slang) a man who both penetrates (top) and is penetrated (bottom) in sex with other men; sometimes also has relationships with women and/or presents masculine as well as feminine mannerisms and appearances.