The area of a
man's body including (on the same side of the body) his armpit and pectoral area in/on which a woman (or
man: not that there's anything wrong with that) can rest her head and often fall asleep.
The charmpit (chest and armpit) is often utilized after intercourse or strange sounds in the house that frighten the woman into making the
man get out of
bed and investigate said frightening sounds.