When you smoke too much weed in a short amount of time resulting in a headache.
It does depend on your tolerance level and how long you have been smoking for.
also depends on you high level which ranges from 1-30 (most highs are around 13)
"dude why are you holding your head like that, math too hard?"
"I got a headlock.... everything is too hard" >.>
Where the woman is on top thrusting ever so gently, just as she comes to the top of the penis head, she squeezes her pussy walls therefore locking the males penis in her vagina.
"Damn that girl has a good headlock"