verb: when one pulls the back of a chair, couch, or loveseat to make the person sitting in the chair fall back backwards and scream like a little girl. Originated in Washington, DC.

A Walstam is a mean, giant Swede who likes to tickle people and flip over the chairs they are sitting in when they are least expecting it. Walstams make rude and inappropriate jokes. Sometimes they're kind of creepy.