flip someone off
1. To turn something off, typically a switch. A noun or pronoun can be used between "flip" and "off." I flipped off the living room light and headed upstairs to bed.
2. To raise the middle finger (a rude gesture of anger or displeasure) at one. A noun or pronoun can be used between "flip" and "off." What are you flipping me off for, I didn't even say anything insulting! I flipped my brother off after he said that he'd never seen a worse basketball player than me.
flip someone offand flip someone out
tv. to give someone the finger. (Collegiate.) Did you flip me off? You better not have. Ernie flipped Tom out, and Tom flattened Ernie. Ah, life in the big city.