Cyniflu Share definition Flag - an illness characterized by an inability to believe anything you hear. . "I phoned the helpline and they told me I had cyniflu, so my doctor has advised me to stay off work until it clears up. I'm not so sure" Cyniflu by bert sofa February 24, 2010 0 0 Get merch Get the Cyniflu mug. Buy Now — $32.95 See more merch