Definition of rattiest:
(adj) :
(figuratively, informal) In poor condition or repair.
(adj) :
Resembling or characteristic of a rat; ratlike.
(adj) :
Infested with rats.
(adj) :
(figuratively, informal) (originally British) Annoyed, bad-tempered, irritable.
(adj) :
(figuratively, informal) (Australia) Crazy, mad; ridiculous; slightly strange, eccentric; also (followed by about, on, or over), attracted to, infatuated with.
(n) :
Synonym of knock down ginger (“prank of knocking on a front door and running away”).