armpit vs axilla

armpit and axilla both are nouns.

Word	Noun	Adjective	Verb	Adverb
armpit	Yes	No	No	No
axilla	Yes	No	No	No

As nouns, armpit and axilla are synonyms defined as:

armpit and axilla: the hollow under the arm where it is joined to the shoulder

Other synonyms of armpit include axillary cavity, axillary fossa.

armpit (noun)	axilla (noun)
the hollow under the arm where it is joined to the shoulder	the hollow under the arm where it is joined to the shoulder