1. To pop one's head up behind or out from within something, in a manner resembling a turtle's head emerging from its shell. Everyone started turtle heading in their cubicles to see where the music was coming from. People around the campsite began to turtle head from their tents to see what was happening.
2. vulgar slang To need to defecate so badly that one's feces begin to come out through the anus involuntarily. I need to find a bathroom now—I'm starting to turtle head! I was turtle heading by the time we finally got to a rest stop.
n. popping up and down in an office cubicle, looking at what’s going on in the rest of the office. (see also prairie dog.) Everybody was turtle heading, trying to see what was happening in Willy’s cubicle.