A compound word formed from "tell", "me" and "no" used as a method to quickly state, "I preemptively acknowledge that you understand the objective, concept and/or action I have just presented to be accepted as an undeniable fact."
PERSON 1: (posts an image of an exquisite horse to a cowboy's Facebook timeline with the caption "tellmeno".)
PERSON 2 (A cowboy): (inner thoughts) That's an exquisite horse.
PERSON 2 (A cowboy): (inner thoughts) That's an exquisite horse.
by minusbaby November 5, 2013