もっともらしい
mottomorashii

i-Adjective

1. plausible; believable

Usually Written in Kana
きみ説明 せつめいはもっともらしいが、筋 すじがちっとも かよってない。
kimino setsumēwa mottomorashiiga sujiga chittomo tōttenai.
Your explanation sounds plausible, but it just doesn't hold water.
i-Adjective

2. solemn; dignified; serious

Usually Written in Kana