jumper vs ski jumper

jumper and ski jumper both are nouns.

Word	Noun	Adjective	Verb	Adverb
jumper	Yes	No	No	No
ski jumper	Yes	No	No	No

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

Other hyponyms of jumper include bounder, leaper, hopper.

jumper (noun)	ski jumper (noun)
(basketball) a player releases the basketball at the high point of a jump	a skier who leaps through the air (especially on a ski jump)
a sleeveless dress resembling an apron; worn over other clothing
a loose jacket or blouse worn by workmen
a small connector used to make temporary electrical connections
a coverall worn by children
a crocheted or knitted garment covering the upper part of the body
an athlete who competes at jumping
a person who jumps