1. A toilet or something used as a toilet, as a trench in the earth; especially, in a military camp, or bivouac area.
2. A public toilet in a military area.
3. Etymology: first recorded about 1297, from Latin latrina, contraction of lavatrina, "washbasin, washroom", from lavatus, past participle of lavare, "to wash" + -trina, a suffix denoting "workplace".

Its reappearance in 1642 is probably a re-borrowing from French; especially, of a privy of a camp, barracks, college, hospital, etc. Latrine rumor, "baseless gossip" (of the kind that spreads in conversations in latrines) is military slang, first recorded in about 1918.