N2 — outside your level filter
Is said whole, with nothing composed onto it and takes no だ/です, so there are no forms to conjugate.
口が堅い
kuchigakataibe discreet, not give away secretsN2expression
Example sentences2
彼は口が堅いので、安心して相談できる。
kare wa kuchi ga katai node, anshin shite soudan dekiru.
He's discreet, so I can consult him without worrying. neutral
あの人、ほんとに口が堅いから信用できるよ。
ano hito, honto ni kuchi ga katai kara shin'you dekiru yo.
That person is really discreet, so you can trust them. casual