What is the meaning of Backside?

The back side of anything, the part opposite its front, particularly:

1. The back side of an estate: the backyard and outbuildings behind a main house, especially an outhouse.

   The back side of an estate: the backyard and outbuildings behind a main house, especially an outhouse.

   A person's buttocks.

   The back side of a page: a verso.

   The reverse or opposite of anything.

   Used other than figuratively or idiomatically: see back,‎ side.

   Approaching an obstacle backward

   Used other than figuratively or idiomatically: see back,‎ side.

   backside

   Source: wiktionary.org