Top Definition
A phrase sometimes used to avoid cursing, sometimes by professors. A similar reference can be found in Matlab using the 'why' command.
When the problem didn't work out as expected, the professor exclaimed, "What the Jack?!"
by Anonymous222999 March 31, 2010

Free Daily Email

Type your email address below to get our free Urban Word of the Day every morning!

Emails are sent from daily@urbandictionary.com. We'll never spam you.

×