A combination of the words "Shit Rig". A person who possesses a 'shit rig' has an unsightly body.
Shrigs are often cited at the beach and festivals.
A Shrig may often not be aware that they do in fact possess a shrig, and thus, take off the singlet and or tshirt to the laughter of others.
Brad: Hey man, have you seen Jabrolta's body?
Old Mate: yeah mate, biggest shrig out