Someone who is addicted to Porn, Masturbates every chance they get, and will fuck anything they see "breedable".
They will fuck anything in sight and look for any reason to be horny, Some examples of a scrag are:
Their gallery is full of furry images and porn.
They masturbate all the time.
And they are just addicted to being called "good boy" and any other term that can be used to refer to them.
Another word for this is "Gooner" or "Goontard", But scrag is more specific to people who find anything in their household or anything they see as "fuckable" or "breedable"
Bro this guy is such a scrag.
My friend's gallery is FULL of porn, what a scrag.