If "eventful" means "filled with exciting or important events," then some antonyms are:
* Uneventful: This is the most direct opposite, meaning lacking in significant events.
* Monotonous: This suggests a dull, unchanging, and boring quality.
* Dull: This implies a lack of excitement or interest.
* Quiet: This suggests a peaceful and undisturbed state, lacking in activity.
* Stagnant: This emphasizes a lack of progress or change.
If "eventful" means "marked by events," then some antonyms are:
* Unremarkable: This implies a lack of anything significant or noteworthy.
* Ordinary: This suggests a commonplace and unexceptional nature.
* Typical: This implies a common occurrence, lacking anything unusual.
The best antonym for "eventful" will depend on the specific meaning you want to convey.