to use porn not belonging to yourself to get off
or essentially piggy backing on the porn some body else took the time and effort to find, purchase, or load
examples of porny backing include:
1. browsing old web history you didnt leave
2. your brother's stash
3. your dad's stash
4. your lesbian sister's stash
guy 1 "hey did you see that great mag i got from my dads stash!"
guy 2 "seriosly bro stop porny backing on your dad its nothing but over weight black chicks eating pie"