To be in an unsober state of mind, and walk aimlessly looking to interact with any and every person in sight. To lose track of the friends you were originally with and find new ones.
"we've had a few beers tonight, have you seen skyler? nope not for a while, hes out larking, probably wont show up for a while, if ever."
To do a Larking is to wander around aimlessly in your workplace, chatting to anyone who will listen to you in order to avoid your duties in your workplace as much as possible.