(1):

(n.) Intermediate space.

(2):

(n.) The bone or cartilage between the radiale and ulnare in the carpus, and between the tibiale and fibulare in the tarsus. It corresponds to the lunar in the carpus, and to a part of the astragalus in the tarsus of man and most mammals.

(3):

(n.) An intervening agent or instrument.