When not referring to the typical slut, skank, whore, etc., "strag" can also mean:
1. A person who hangs around the neighborhood not doing anything productive.
2. A person who goes to the local McDonald's, orders dollar menu fries, and then hangs around in the back of the restaurant with his/her friends for the next six hours.
3. To leave the house with no destination only to end up sitting on the swings in the local playground at 10 PM even though you're like 17.
A: "I'm bored. I'm going out for a walk."
B: "Where are you going?"
A: "I don't know."
B: "What a strag."
A: "I was working at McDonald's today and ten kids came in, ordered one thing of fries, and then sat there for the rest of the night."
B: "Sounds like you were invaded by strags."
A: "I'll be back around midnight, I'm going out stragging."