Lewis Short
insessor (noun M) : id.
* A besetter, occupant (very rare); of a ship,Jul. Val. Res Gest. Alex. 1, 1: viarum,a waylayer,Symm. Ep. 2, 48; cf.: insessores, latrones, Paul. ex Fest. p. 111 Müll.: quod circa vias insidientur sedentes.
Charlton T. Lewis, Charles Short, A Latin Dictionary