"A bluff is a bet you make when you dont want a caller".
You are playing NLHE and have somehow misjudged your preflop raise, perhaps with a misclick.
You hold AK and the flop comes Kxx 2 hearts. Your single opponent turns his cards over and shows you a flush draw. He doesnt particularly understand the odds and after the flop, he will call when ahead and fold when behind. You turn your cards over and move allin for 1/10 of the pot.
Is this a bluff?