surgical operation vs trepan

surgical operation and trepan both are nouns.

Word	Noun	Adjective	Verb	Adverb
surgical operation	Yes	No	No	No
trepan	Yes	No	Yes	No

surgical operation (noun)	trepan (noun)
a medical procedure involving an incision with instruments; performed to repair damage or arrest disease in a living body	a drill for cutting circular holes around a center
	a surgical instrument used to remove sections of bone from the skull

surgical operation (verb)	trepan (verb)
	cut a hole with a trepan, as in surgery