Lewis & Short

sĕnīlis, e, adj. [senex], of or belonging to old people, aged, senile (freq. and class.): Tages puerili specie dicitur visus, sed senili fuisse prudentiā, Cic. Div. 2, 23, 50; cf. partes (opp. viriles), Hor. A. P. 176: senile aliquid (opp. adulescentis aliquid), Cic. Sen. 11, 38: corpus, id. Sest. 22, 50: artus, Ov. M. 7, 250: vultus, id. ib. 8, 528: genae, id. ib. 8, 210: guttur, Hor. Epod. 3, 2: ruga, Ov. F. 5, 58: statua incurva, of an old man, Cic. Verr. 2, 2, 35, § 87: anni, Ov. M. 7, 163; 13, 66; and poet.: hiems (as the last, latest season of the year), id. ib. 15, 212: animus, Liv. 10, 22: stultitia, Cic. Sen. 11, 36: auctoritas morum, Quint. 11, 1, 32: artes, Tac. A. 3, 8: adoptio, id. ib. 1, 7 fin.: senile illud facinus, that wicked old woman, App. M. 4, p. 148, 9.
* Adv.: sĕnīlĭter, after the manner of an old person: tremere, Quint. 1, 11, 1.