crab apple vs wild apple

crab apple and wild apple both are nouns.

Word	Noun	Adjective	Verb	Adverb
crab apple	Yes	No	No	No
wild apple	Yes	No	No	No

As nouns, crab apple and wild apple are synonyms defined as:

crab apple and wild apple: any of numerous wild apple trees usually with small acidic fruit

Other synonyms of crab apple include crabapple.

crab apple (noun)	wild apple (noun)
small sour apple; suitable for preserving	any of numerous wild apple trees usually with small acidic fruit
any of numerous wild apple trees usually with small acidic fruit
any of numerous varieties of crab apples cultivated for their small acidic (usually bright red) fruit used for preserves or as ornamentals for their blossoms