Definitions by Dr. DJ

Vai 

A morning erection that is naturally caused as the brains enters the REM-deep sleep phase. At this stage, the body's skeletal muscle structure relaxes and causes hypervasodilation in the capillaries of the body, resulting in solid erection.

After sleeping so soundly and having a great night's rest, it is no surprise to wake up with a vai.

Vai by Dr. DJ December 7, 2011