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A delay in reaction time causing one to resemble a high latency video-game character. It is often accompanied by a distorted perception of time, short term memory loss, extreme clumsiness, and loss of depth perception.

Body lag is generally the product of Alcohol and/or lack of sleep.
"I had to get up at three in the morning on one hour of sleep, my body lag was so bad that I ran into my bedroom door on the way out after I thought I had opened it."
by Droolguy September 25, 2011