Signalling to another via the medium of text the fact you are carrying out an action, in this case, the movement of raising the shoulders, which highlights the point you are basically saying 'I don't know' or 'whatever' but in a non-verbal manner.
Rob: Guys who is the coolest person ever?
Jen: *shrug*
Pete: *shrug*
Fred: *shrug*
Greg: I KNOW! I KNOW! It has to be rob!
Rob: Yes Greg. Yes it is.
By Pearl
Shrugged
To raise your shoulder and then lower them to show that you do not know or care about sth:
Shrugs are all the rave among teenage girls. These alleged pieces of clothing provide neither warmth nor coverage. It also fails to increase the perception of chest size. The title derives from the action spurred by a girl wearing it. You shrug because you have no idea what it is for.
When I woke up in Spanish class today, I was surrounded on eight sides by girls wearing shrugs. I could only help but shrug.
By Alfie
Shrugness
Used in addition with "idk" when someone does not know what to say.
When you make a thinly veiled attempt at weaving your way out of a situation/meeting someone/fulfiling an obligation. Some people do this more than others, and can develop a reputation for it.