undescended testis vs bollock

undescended testis and bollock both are nouns.

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

As nouns, bollock is a hypernym of undescended testis; that is, bollock 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
bollock: one of the two male reproductive glands that produce spermatozoa and secrete androgens

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

undescended testis (noun)	bollock (noun)
a testis that fails to move into the scrotum as the male fetus develops	a pulley-block at the head of a topmast
	one of the two male reproductive glands that produce spermatozoa and secrete androgens