A fail cone becomes a fail cone when the ice cream put on a cone fails to look like a good ice cream cone, and instead comes out to be a glob of ice cream on top of a cone.
One who makes a fail cone will never admit that they make a fail cone because they believe that their cone looks great, even though the ice cream is clearly lopsided or not twisted properly. They may also try to cover up the glob with some colorful sprinkles or toppings to distract any other viewers from noticing the fail cone. But do not be deceived, a fail cone still exists even if it is hidden under pretty toppings.
Once pointed out, a fail cone will be eaten very quickly, especially if the one who is planning on eating it was the one who made it.
Note: This term can only be used to describe soft serve ice cream cones.
Customer: "Hey can I get chocolate ice cream on a cone?"
Waiter: "Sure, hold on one moment."
(Waiter hands customer his cone, with the ice cream all in a big glob on top of the cone rather than a nice swirl)
Customer: "What is this? This isn't an ice cream cone! This is a fail cone!"
Person 1: "Hey what do you have there?"
Person 2: "Oh I just made an ice cream cone"
(Person 1 takes a look at the cone: a regular sugar cone, with some ice cream on top, but it is all smooshed, and there is a notable amount of sprinkles on top)
Person 1: "Ice cream cone? More like fail cone!"