axillary cavity axil·la·ry·cavity uncommon noun 1. the hollow under the arm where it is joined to the shoulder “they were up to their armpits in water” Synonymsarmpitaxillaaxillary cavityaxillary fossa Related words Broader terms cavity Parts shoulder Part of axillary artery WordNet 2.1 (Princeton University). WordNet 2.1 Copyright Princeton University. All rights reserved.
