drill vs trepan

drill and trepan both are nouns.

Word	Noun	Adjective	Verb	Adverb
drill	Yes	No	Yes	No
trepan	Yes	No	Yes	No

As nouns, trepan is a hyponym of drill; that is, trepan is a word with a more specific, narrower meaning than drill:

drill: a tool with a sharp point and cutting edges for making holes in hard materials (usually rotating rapidly or by repeated blows)
trepan: a drill for cutting circular holes around a center

As verbs, trepan is a hyponym of drill; that is, trepan is a word with a more specific, narrower meaning than drill:

Other hyponyms of drill include spud, counter-drill.

drill (noun)	trepan (noun)
systematic training by multiple repetitions	a drill for cutting circular holes around a center
(military) the training of soldiers to march (as in ceremonial parades) or to perform the manual of arms	a surgical instrument used to remove sections of bone from the skull
similar to the mandrill but smaller and less brightly colored
a tool with a sharp point and cutting edges for making holes in hard materials (usually rotating rapidly or by repeated blows)

drill (verb)	trepan (verb)
learn by repetition	cut a hole with a trepan, as in surgery
teach by repetition
train in the military, e.g., in the use of weapons
undergo military training or do military exercises
make a hole, especially with a pointed power or hand tool