Litotes - Expressing a positive by negating a negative, from a Greek word litos, meaning "plain." The beauty of a litotes is its subtlety and nuance; it's not exactly a ringing endorsement to say someone's "not incompetent," or the a meal's "not bad." It can also be a mildly humorous method of understatement. "Nec pluribus impar," "Not unequal to most," was the motto of Louis XIV, whose other sobriquets were Louis the Great, the Sun King, and who also is famed to have said, "L'etat cest moi," "The state, it is I." Because double negatives are creeping into our language as a means of emphasis, litotes are losing their effectiveness and clairity. (An Eighteenth Century grammarian would have taken "You're not going nowhere!" to mean you are going somewhere. Now it just means you're really not going.) James Thurber's playful litotes, "not unmeaningless," takes so many steps to decode, we don't realize for a bit it doesn't mean anything. But that's the idea.