Lewis Short
(adjective) : spĕcŭlābundus, a, um, id.
* On the look-out, on the watch; watching for any thing (post-Aug.): Festus Hadrumeto, ubi speculabundus substiterat, etc.,Tac. H. 4, 50: ab ostio speculabunda,Mart. Cap. 2, § 112.—With acc.: speculabundus ex altissimā rupe identidem signa,Suet. Tib. 65.
Charlton T. Lewis, Charles Short, A Latin Dictionary