The act of denying a duty or responsibility,thus leaving it to others. When one calls "no whammy", on something, he/she is refusing to take responsibility for it. The last person in the group to call "no whammy" is he/she whom,by default, takes responsibility of the proposed issue or action.
"No Whammy on sitting next to Jacob!"
"No Whammy on driving!"
"Hey,I called No Whammy on the aisle seat so you have to sit there!"