- The definition of backside is the rump of a human or the hind part of an animal.
If you slip on ice and fall on your rear end, then that is an example of falling on your backside.
A dogs backside.
backside definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
- the back or hind part
- the rump; buttocks
Origin: Middle English bak side
backside definition by American Heritage Dictionary
The buttocks; the rump.