Definitions
1.NounThe back side of anything, the part opposite its front, particularly:
The back side of an estate: the backyard and outbuildings behind a main house, especially an outhouse."The building's backside faced an alley and was covered in grime and graffiti.; Having ridden the horse all day for the first time, I had painful blisters on my backside."
2.NounThe back side of an estate: the backyard and outbuildings behind a main house, especially an outhouse."The building's backside faced an alley and was covered in grime and graffiti."
3.NounA person's buttocks."Having ridden the horse all day for the first time, I had painful blisters on my backside."
4.NounThe back side of a page: a verso.
5.NounThe reverse or opposite of anything.
6.NounUsed other than figuratively or idiomatically: see back, side.
7.AdjectiveApproaching an obstacle backward.