1. [informal] The fleshy part of the human body that you sit on
   "he deserves a good kick in the backside";
   - buttocks, nates [informal, technical], butt [N. Amer, informal], bum [Brit, informal], buns [N. Amer, informal], can [N. Amer, informal], fundament [informal], hindquarters [informal], hind end [informal], posterior [informal], rear [informal], rear end [informal], rump [informal], stern [informal], seat [informal], tail [N. Amer, informal], tail end [informal], tooshie [informal], tush [N. Amer, informal], bottom [informal], behind [informal], derriere [informal], patootie [US, informal], botty [informal], duff [N. Amer, informal], bahookie [UK, dialect, informal], booty [N. Amer, informal], heinie [US, informal], tushy [N. Amer, informal], derrière [informal]
    
2. The side of an object that is opposite its front
   "his room was toward the backside of the hotel";
   - rear, back end

Derived forms: backsides

Type of: body part, face, side

Part of: body, torso, trunk

Encyclopedia: Backside