someone who cleans their butt from the side by lifting a right or left cheek, rather than between their legs or between their balls (centerwiper)
Bro, do you wipe your ass from the center between you balls?
Naw bro, I'm a Sidewiper... I lift a cheek, yo.
Someone who continues to do something as they were taught even after knowing/seeing a much better method. A person who wipes their ass sideways cheek to cheek instead of up or down between the cheeks.
That guy stinks like shit, he must be a sidewiper.
A person who had skid marks in their pants but wiped sideways causing said sidewipe marks.
Hence sidewipe
Oh you little shit. You are a sidewipe