AXILLA

armpit, axilla, axillary cavity, axillary fossa

(noun) the hollow under the arm where it is joined to the shoulder; “they were up to their armpits in water”

Source: WordNet® 3.1

Etymology

Noun

axilla (plural axillae)

The armpit, or the cavity beneath the junction of the arm and shoulder.

(botany, uncommon) Alternative form of axil

Source: Wiktionary

Ax*il"la, n.; pl. Axillae. Etym: [L.] (Anat.)

Definition: The armpit, or the cavity beneath the junction of the arm and shoulder.

2. (Bot.)

Definition: An axil.

Source: Webster’s Unabridged Dictionary 1913 Edition