1. Game played in the classroom.
2. Describes the posture of people sending SMS's, tweets, emails, facebook status, ebay, blogs etc.
3. A good way to miss your turn-off, walk into someone or have a crash
John: Hey Lisa, check out Jeff...
Lisa: Yeah, he's breaking up with Kate...he's been heads
up all day
John: Hey Lisa, what's with the heads down thumbs up?
Lisa: oh, I'm tweeting
how lame my friends are...