adj; a: A person who leaves someone waiting indefinitely without sufficient notice if any. b; Someone who lives in a flat and exits said flát.
A: A Flatleaver is one of two or more friends who make plans to go out and the one friend who never shows or calls to cancel!
B: A flat is an apartment in other parts of the world. Therefore. A Flatleaver is someone who is in a flat and exits said flat.