crest vs upside

crest and upside both are nouns.

Word	Noun	Adjective	Verb	Adverb
crest	Yes	No	Yes	No
upside	Yes	No	No	No

As nouns, upside is a hypernym of crest; that is, upside is a word with a broader meaning than crest:

Other hypernyms of crest include top, top side, upper side.

crest (noun)	upside (noun)
a showy growth of e.g. feathers or skin on the head of a bird or other animal	the highest or uppermost side of anything
(heraldry) in medieval times, an emblem used to decorate a helmet
the center of a cambered road
the top line of a hill, mountain, or wave
the top or extreme point of something (usually a mountain or hill)

crest (verb)	upside (verb)
reach a high point
lie at the top of