WordNet sense 1 (a small third seat in the back of an old-fashioned two-seater):

dickey, dickey-seat, dickie, dickie-seat, dicky-seat

WordNet sense 2 (a man's detachable insert (usually starched) to simulate the front of a shirt):

shirtfront

WordNet sense 3 (diminished in strength, quality, or utility):

impaired