A dogs backside.
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.
- the back or hind part
- the rump; buttocks
Origin of backside
Middle English bak side
The buttocks; the rump.
- The side of something that is opposite the front.
- The backside of the building faced an alley, and was covered in grime and scrawled graffiti.
- The buttocks.
- After riding the horse all day for the first time, I had painful blisters on my backside.