Lewis Short
(verb) : ex-dorsŭo or -dorso, āre, dorsum; lit., to deprive of the back; hence, in partic., of fishes
* To take out the backbone, to bone (ante- and post-class.): congrum, muraenam exdorsua, quantum potes,Plaut. Aul. 2, 9, 2: pisces (with desquamare),App. Mag. p. 301, 3; cf.: exdorsuare, dorso nudare,Non. 17, 29: exdorsua dorsum confringe; alii, exime, Paul. ex Fest. p. 79, 12 Müll.
Charlton T. Lewis, Charles Short, A Latin Dictionary