Snowboarding
In snowboarding, frontside and backside have the same meanings as in skateboarding. When turning, backside is analogous to a toeside turn, and frontside is analogous to a heelside turn.
In the air, backside means that you turn the front of your body into the rotation first and frontside means you turn your back into the rotation first. For example, a left foot forward (or regular) rider would rotate counterclockwise to do a frontside 360 and clockwise to do a backside 360.
Read more about this topic: Frontside