sleeper vs dreamer

sleeper and dreamer both are nouns.

Word	Noun	Adjective	Verb	Adverb
sleeper	Yes	No	No	No
dreamer	Yes	No	No	No

As nouns, dreamer is a hyponym of sleeper; that is, dreamer is a word with a more specific, narrower meaning than sleeper:

sleeper (noun)	dreamer (noun)
an unexpected hit	a person who escapes into a world of fantasy
tropical fish that resembles a goby and rests quietly on the bottom in shallow water	someone guided more by ideals than by practical considerations
a passenger car that has berths for sleeping	someone who is dreaming
one of the cross braces that support the rails on a railway track
a piece of furniture that can be opened up into a bed
pajamas with feet; worn by children
a rester who is sleeping
an unexpected achiever of success
a spy or saboteur or terrorist planted in an enemy country who lives there as a law-abiding citizen until activated by a prearranged signal