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1. Jack Mode
To go into a stealing frenzy. From the word jack (as in to steal). Literally "stealing mode". Often yelled as one steals something in a very obvious manner.

See jack
"Jack Mode!" *runs off with object*
by n00bdragon Dec 7, 2004 add a video
2. jack mode
When you're so angery that you could be considered a possible homocide offender.
Comes from the saying: Jack's got the key to the gun case. Wanna see?
I was in Jack mode when Daniel's project got a higher grade than mine.
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