The Collaborative International Dictionary of English v.0.48:
dickie-seat \dickie-seat\ n. 1. A small 3rd seat in the back of an old-fashioned 2-seat car. [British English] Syn: dickey, dickie, dicky, dickey-seat, dicky-seat, dickey box. [WordNet 1.5]WordNet (r) 3.0 (2006):
dickie-seat n 1: a small third seat in the back of an old-fashioned two- seater [syn: dickey, dickie, dicky, dickey-seat, dickie-seat, dicky-seat]