backseat vs dickey-seat

backseat and dickey-seat both are nouns.

Word	Noun	Adjective	Verb	Adverb
backseat	Yes	No	No	No
dickey-seat	Yes	No	No	No

As nouns, dickey-seat is a hyponym of backseat; that is, dickey-seat is a word with a more specific, narrower meaning than backseat:

backseat: a seat at the back of a vehicle (especially the seat at the back of an automobile)
dickey-seat: a small third seat in the back of an old-fashioned two-seater

Other hyponyms of backseat include dickey, dickie-seat, dickie, dicky-seat, dicky.

backseat (noun)	dickey-seat (noun)
a seat at the back of a vehicle (especially the seat at the back of an automobile)	a small third seat in the back of an old-fashioned two-seater
a secondary or inferior position or status