Final answer:
An antonym for 'optimistic' is 'bleak' which means lacking optimism or hope. Other antonyms include 'angry', 'positive', and 'happy'.
Step-by-step explanation:
Antonyms are important for enriching vocabulary and providing nuances in language. They are often used to express shades of meaning and to create contrast or opposition in writing and speech.
An antonym for optimistic is bleak. While optimistic refers to having a positive or hopeful outlook, bleak means lacking optimism or hope.
Other antonyms for optimistic include angry, positive, and happy. These words represent different emotions or attitudes that are opposite to being optimistic.