Things that are antifragile grow and strengthen from volatility and stress (to a point). When people or systems are antifragile, there’s more upside than downside when Black Swan events occur. Antifragile systems feed on chaos and uncertainty like a primordial god.
Taleb likens antifragility to the Hydra from Greek mythology. The Hydra was a hideous multi-headed lizard monster. Whenever a hero cut off one of the Hydra’s heads, two would grow back in its place — the Hydra became stronger with adversity.