dickey-seat vs backseat

dickey-seat and backseat both are nouns.

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

As nouns, backseat is a hypernym of dickey-seat; that is, backseat is a word with a broader meaning than dickey-seat:

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

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