When someone is smiling for an extended period of time, in most cases nothing was even funny and the person is standing by themselves looking like they are saying cheeze or "cheezin" for a picture.
Sean- Yo, look at Floyd over there cheezin
Tom- I know, i hate that kid, hes such a loser, he chills by himself and just smiles for no fucking reason
*edward calls up his friend jeremy
edward:"watcha doin"
jeremy:"cheezin"
edward:"what?"
jeremy:"u know,chill'in"
edward:"yea but, we have a test tomorow at school"
jeremy:"i dont feel like studying today"
edward:"this is the most important test this year at school"
jeremy:"whatever"
*edward hangs up