Unconvincing (adjective)

Not able to persuade or convince someone that something is true or valid.

Origin:

The word "unconvincing" comes from the late middle english word "unconvins", which means not convincing. the word "convins" comes from the latin word "convincere" which means to conquer, overcome or prove.

Examples:

1. The prosecution's case was unconvincing and the jury acquitted the defendant.
2. The argument that he gave was unconvincing and did not make sense.
3. His performance was unconvincing and I couldn't take him seriously.
4. Her story was unconvincing and I didn't believe a word she said.
5. The evidence presented was unconvincing and the judge declared a mistrial.