Too many factors to give a definitive answer on this one.
Location of the grab has to be taken into consideration as well. If it's in an erogenous zone, then I hope you've got an understanding with the grabber.
Also depends on how close your relationship is to the grabber. Are you friends, or more? If they're your Uncle - then tell your parents. If it's your Dad and it's unwelcome and uncomfortable - tell your Mum or the police.
It means he has a crush on that girl.
if a guy grabs you by hand then it simply means that he is attracted to either physically or even sexually.it may not be necessary for him to like you
He likes you
"But does this with other girls...." No. You are nothing special.
Playful love
When a guy moves his head from resting on your knee higher to you thigh, then your pelvis, he is being suggestive, and stop him if you are uncomfortable with it.
That would be a pretty clear sign that he likes you.
When she has a muscle that grabs your private parts and want let go till she is ready
He loves u avcorse and ur hot and he can not stay away from u
It may mean that this person is in an experimental phase of their life. They may be gay or bi-sexual.
Probably
Differs from guy to guy, however, most guys like nice girls.