to be used in situations of extreme sarcasm, apathy, or general indifference. can also be used to express boredom or as a substitute for "whatever", "true" or "true story", "cool", "nice", or "meh".
Extreme sarcasm: "i guess that kid that killed himself really wanted to live shrug"
Extreme apathy: "if you dont want to live anymore why dont you just get hit by a bus shrug"
General indifference: "woke up hungover today shrug"