Could also be a potential boyfriend or girlfriend whom you like then before you even approach him/her you find out something awful about him/her that you cannot stand, you automatically disqualify them from being your boyfriend or girlfriend before you even talk to him/her.
James: " Yeah she is hot. You don't know Mary? She used to be a man then dated a rich guy who paid for her sex change."
John: What? For real? She is pre-disqualified then!