checking the dipstick

When a girl fingers a guy's asshole while sucking you off.

Man, Kim is a crazy bitch! The other night she was checking the dipstick.

Check your dipstick

When one either passes gas and is not sure if it was a shart, or they might not have wiped good enough earlier after pooping, takes toilet paper and dry wipes their butt.

Phil was so sweaty and didn’t know if he wiped good enough earlier, so I told him to check your dipstick.