General Antonyms:
* Blunt: Lacking sharpness or perceptiveness.
* Dull: Lacking interest, excitement, or sharpness.
* Indifferent: Not caring or interested.
* Apathetic: Showing or feeling no interest, enthusiasm, or concern.
* Uninterested: Not interested or concerned.
Antonyms Related to Specific Meanings:
* Obtuse: Not sharp or pointed (referring to intelligence or understanding).
* Unenthusiastic: Lacking enthusiasm or eagerness.
* Reluctant: Unwilling or hesitant.
* Averse: Having a strong dislike or aversion.
* Unwilling: Not wanting to do something.
Example:
* Keen: "She was keen to learn more about the project."
* Antonym: "He was uninterested in the project and showed no enthusiasm."
The best antonym depends on the specific meaning of "keen" in the context.