ARMPIT
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
armpit (plural armpits)
The cavity beneath the junction of the arm and shoulder.
Somewhere or something considered unpleasant or undesirable.
Synonyms
• (cavity beneath the junction of the arm and shoulder): axilla, oxter, underarm; armhole (now UK dialect)
Coordinate terms
• poplit (“knee pit”)
Anagrams
• Primat, impart
Source: Wiktionary
Arm"pit`, n. Etym: [Arm + pit.]
Definition: The hollow beneath the junction of the arm and shoulder; the
axilla.
Source: Webster’s Unabridged Dictionary 1913 Edition