Unconvincing means failing to make people believe it. An unconvincing excuse.
It judges the effect rather than the truth, so something true can be unconvincing. An unconvincing denial does more damage than saying nothing at all.
1adjectiveunconvincingFailing to make people believe it.
“The explanation was unconvincing and the questions started again.”
unconvincing is a quality.
From un- + convincing.
Etymology from Wiktionary, CC BY-SA