To have your backpack turned inside out and all your books placed inside it, so you can no longer wear it but must carry it around.

Let me die.

The act of a man's penis being extremely flaccid and no longer visible.

to knock out an obese person and they fall on their back, the sleeping "turtle's" back fat makes them rock side to side

when receiving oral sex and then your legs get lifted and the person starts eating your ass leaving you stuck on your back with your anus in the air (like a turtle).

To be so completely drunk that once fallen over and are lying on the ground, one cannot pick themselves up and requires help,akin to a turtle which is helpless when placed upside down on its back