Lewis Short
(adjective) : immūnītus (inm-), a, um, 2. in-munitus
* Unfortified, undefended (rare but class.): oppida castellaque,Liv. 22, 11, 4: Sparte,Ov. M. 10, 169: inermes atque immuniti abscondimus,App. M. 8, p. 202 fin.: via,i. e. not properly made, impassable,Cic. Caecin. 19, 54.
Charlton T. Lewis, Charles Short, A Latin Dictionary