“Protego Totalum. . . Salvio Hexia. . . Cave Inimicum. . . "
-- Hermione Granger casting protection spells (DH22)
Cave Inimicum is the incantation for a defensive spell which keeps enemies away.
References from the canon
This protective spell was cast by Hermione around the tent and campsite when the trio was on the run (DH14, 22).
“cave” L.: beware + “inimicum” L.: enemies
From the Web
"Cave Inimicum" from Harry Potter Wiki