Someone who is "all there" in a mental sense but not necessarily in a physical one.
Steven Hawking is totally screwed on man.
Beküldő: Simon Batt 2005. január 12.
1 more definition
Opposite to someone who has a screw loose i.e a bit dopey.
You obviously had your head screwed on while you were tackling that piece of coursework.
Beküldő: Simon Batt 2005. január 13.