noun.
A body part analogous to the armpit, such as the hollow under a bird's wing.
The Century Dictionary and Cyclopedia
noun.
In anatomy, the armpit; a region of the body in the recess between the upper arm (or in birds the upper part of the wing) and the side of the chest beneath the shoulder.
noun.
In botany, same as axil, 2.
the GNU version of the Collaborative International Dictionary of English
noun.
The armpit, or the cavity beneath the junction of the arm and shoulder.