A state of temporary immunity used in playground games. This immunity is initiated by a number of methods, the most common involving sticking your thumbs in the air and simply shouting "Keezees!". Thus, you are exempt from whatever game is being played, and are immune from being picked, "tagged", etc.
*bends down to tie shoe-laces as "it" person approaches*
"Ah'm keezees, by the way! Ye canny tag me!"
*"it" person slopes off dejected, in search of another victim*