Inconsistent (adjective)

1. Not in agreement or harmony with each other.
2. Not able to be reconciled or made consistent.
3. Not behaving or performing in a consistent or predictable way.

Origin:

From latin inconsistentem, present participle of incōnsistere ("to be inconsisten.t")

Examples:

1. The witness's testimony was inconsistent with the evidence.
2. The results were inconsistent and couldn't be trusted.
3. His behavior was inconsistent and hard to predict.
4. The team's performance was inconsistent throughout the season.
5. Her actions were inconsistent with her words.