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1 definition by Scott the Heirophant

 
1.
"Half Jack" refers to a person who is gender confused, and possibly considering sex change surgery. A person who either feels that they are of the wrong gender, or that they are half male and half female.
Mary was really into Tom at the party last night, but she wasnt aware that he's "Half Jack" and had no interest in her.
by Scott the Heirophant February 09, 2008