Lewis Short
(verb) : sĕneo, ēre, v. senex.
* Lit., to be old (very rare; perh. only in the foll. examples): quamquam aetas senet, Pac. ap. Prisc. p. 887; Cat. 4, 26.
* Transf., to be weak, feeble: corpus meum tali maerore, errore, macore senet, Pac. ap. Non. 137, 1; (with languere) Att. ap. Prisc. p. 887 P.
Charlton T. Lewis, Charles Short, A Latin Dictionary