a phrase used by every white Australian male PE teacher when you fuck around.
you're better off to stop being fucking annoying or they'll call you fuckwit for the rest of the year.
The action used immediately before a fart when you nonchalantly pull on one buttcheek in an effort to spread the anus and thus prevent the fart from making noise.
get on with it; stop wasting time shortened form of "pull your finger out of your ass"
(apparently, having your finger up your ass interferes with efficiency)