when someone tries to rectify another's actions without knowing what happened.
dude: hey, go easy on him. he was probably just drunk and decided to go for a swim.

guy: hey, you weren't there, stop trying to guestify him.
by Jazzy Lee Sargent August 22, 2008
You nickname account has been change to the guest user account because you failed to indentify yourself within a set time, due to the requirement of a valid email address on IRC's new nickserv user account server.
"My account has been guestified"
by P£MBY December 4, 2003