To have fun, frolic and romp about in a slightly mischievous way.

When someone goes to the gym and spends 90% of the time on their phones scrolling through social media

When someone does a harmless prank.

When you don't have anything particular in mind, but are looking for an entertaining adventure.

To be silly and playful.

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.

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.