undescended testis vs testis

undescended testis and testis both are nouns.

Word	Noun	Adjective	Verb	Adverb
undescended testis	Yes	No	No	No
testis	Yes	No	No	No

As nouns, testis is a hypernym of undescended testis; that is, testis is a word with a broader meaning than undescended testis:

undescended testis: a testis that fails to move into the scrotum as the male fetus develops
testis: one of the two male reproductive glands that produce spermatozoa and secrete androgens

Other hypernyms of undescended testis include ball, ballock, bollock, egg, nut, orchis, testicle.

undescended testis (noun)	testis (noun)
a testis that fails to move into the scrotum as the male fetus develops	one of the two male reproductive glands that produce spermatozoa and secrete androgens