unconvincing

not convincing, plausible or believable

Japanese Meaning

説得力に欠ける / 信じがたい / 納得させない

Her explanation for missing the meeting sounded unconvincing to everyone in the room.

会議を欠席した理由の説明は、部屋の全員にとって説得力がなかった。

Sense（1）

not convincing, plausible or believable

He gave me an unconvincing explanation of the fault, but I have my doubts.

more unconvincing

（ comparative ）

most unconvincing

（ superlative ）