Top Definition
The substantial and long-sustained decrease in intelligence and social aptitude test scores measured in many aspects of one's life starting roughly the time they become friends with a particular individual. There is no cure for the Williams Effect.
My friends tell me my social sensibilities have decreased upon moving in with my roommate. #TheWilliamsEffect

I thought I was immune to the Williams Effect until I found myself discussing MMA and WWE wrestling after a few short weeks of hanging with Alex.
by SheldonMCohen February 08, 2013

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