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The annoying habit of having to visit the restroom before going out. Results in tardy lunch dates and annoyed companions. Generally a wallgren is pulled, as in "pull a wallgren".
Pat: Dude, wait up. I have to pull a wallgren.

Jim: Damn it. We're gonna be late for batting practice.
by WS February 03, 2004
One who acts in various states of dorkiness throughout the day. A typical Wallgren hangs out with Asians in the hope of absorbing some intelligence, but instead usually gets justifiably picked on.
Dude, you're such a Wallgren. (said to a blond loser getting beat up by an Asian gang).
by A.S. January 31, 2004