• WordNet 3.6
    • n cubitus the arm from the elbow to the fingertips
    • n cubitus hinge joint between the forearm and upper arm and the corresponding joint in the forelimb of a quadruped
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Century Dictionary and Cyclopedia
    • n cubitus Same as cubit.
    • n cubitus In ornithology, the forearm; more particularly the ulna, or outer bone of the forearm.
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In literature:

Anal furrow: in wings, lies between the cubitus and 1st anal vein.
"Explanation of Terms Used in Entomology" by John. B. Smith