insidiator

insĭdĭātor, ōris, m. [insidior],

I a soldier lying in ambush , Hirt. B. G. 8, 18.—

II Transf., one who lies in wait , a lurker , waylayer (rare but class.): viae, Cic. Cat. 2, 12, 27: in foro collocatur, id. Mil. 7, 19: imperii, Nep. Reg. 2.