Wiktionary
n. 1 The relatively high probability of a relatively extreme outcome. 2 (context statistics probability English) A tail of a probability distribution with significantly higher kurtosis than a normal distribution (which has kurtosis = 0). 3 (context statistics probability English) A tail of a probability distribution with infinite variance.
Usage examples of "fat tail".
The crowd held its breath as the small cat leapt over Horace, barely skimming the proud flag flying off that fat tail.
If you turn back no later than 1400 hours, Little Eva's outer breeze should provide you with a nice fat tail wind to nudge you home.
Piedmont meowed and butted her in the ribs, then walked prickly-pawed across her lap, slinking his fat tail beneath her chin.
The creature it rode resembled nothing so much as a huge lizard with fat, kneeless legs and a long, fat tail.
The Hutt thumped his fat tail on the stone platform, dismissing them.
The creature was a third of a metre long from the forked-tongued snout to the end of the fat tail.