A person who habitually sees the worst aspect of things; a somewhat formal or literary term.
He is a pessimist and always predicts the worst outcomes.
Compound of 厭世 (world-weariness) + 悲観 (pessimism) + 者 (person). The exact historical derivation is uncertain, but the components transparently combine to mean 'a person who is weary of the world and pessimistic'.