Toothin has many meanings.
It usually means chilling or relaxing.

This saying recently became popular on sites such as facebook. It is short for roostertooth. Also abriviated RT.

It's the new thing. Often used with a hashtag.
Hey whatsup?
Toothin', you?

no ! ramによって 2011年11月15日(火)
To use bluetooth technology with a cell phone
Look an Nate; He is toothin'!
Matthew Demarestによって 2006年08月03日(木)