*coworker observes me with yarn and needles* Coworker: What're you knitting?
Me: *after a moment's thought* Well, it's a yarn bomb.
Coworker: It's a tri- what?
Me: Yarn bomb!
Coworker: What are yarn bombs for?
Me: Welllll.... You take it, attach it to a piece of property that is not your own, and then you run away.
Coworker: *looking puzzled* It's what now?
Me: It's graffiti.
Coworker: *understanding dawning* Coooool....
Me: And it doesn't actually destroy anyone's property, so there's that.
Coworker: Oh. Yeah. That's a lot better.