noun
A philosophical or general outlook that expects the worst outcome. Often contrasted with 楽観主義 (optimism).
彼の悲観主義は、周りの人にも影響を与えている。
His pessimism is affecting the people around him.
悲観主義に陥ると
When you fall into pessimism, you can't get anything done.
Compound of 悲観 (pessimistic view) + 主義 (principle, -ism). 悲観 is itself a Sino-Japanese word composed of 悲 (sad, mourn) and 観 (view, outlook).