concăvo, no perf., ātum, 1, v. a. [concavus],
to make hollow, to hollow out, make round (very rare): bracchia in arcus, to curve, bend , Ov. M. 2, 195; cf. manus, Nemes. Ecl. 3, 49: concavati nidi, Col. 8, 5, 11.
concavō —, ātus, āre, to make hollow, round, curve: bracchia in arcūs, O. ...
An Elementary Latin Dictionary