Have a big mouth：”kuchi ga karui” Japanese Phrase #273

Yuka

Today’s expression — 口が軽い — is a great idiom to know! Let’s find out what it means and how to use it.

What Does 口が軽い Mean?

口が軽い literally means “mouth is light.” Figuratively, it describes someone who talks too much — especially someone who can’t keep secrets or gossips easily.

Think of it like: “their mouth is so light, words just float out.”

Example Sentences

• 彼は口が軽いから、秘密は話せない。 — He has a big mouth, so I can’t tell him secrets.
• あの人、口が軽すぎて困る。 — That person talks too much — it’s a problem.
• 口が軽い人には注意して。 — Be careful around people who can’t keep secrets.

Rei

What about the opposite — someone who DOES keep secrets?

Yuka

That’s 口が固い (kuchi ga katai) — “mouth is firm/hard.” You can trust them with secrets!

The Full Mouth Idiom Set

Quick Quiz

Which word fits? “I told him in confidence, but he’s ___ so he told everyone.”

• a) 口が固い
• b) 口が軽い
• c) 口が重い

Answer: b) 口が軽い — he couldn’t keep the secret.

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