口くちがうまい

く

ち

が

う

ま

い

口がうまい · i-adjective

Form	Positive	Negative
Dictionary	口くちがうまい	口くちがうまくない
Polite	口くちがうまいです	口くちがうまくないですalso 口くちがうまくありません
Past polite	口くちがうまかったです	口くちがうまくなかったですalso 口くちがうまくありませんでした
Past	口くちがうまかった	口くちがうまくなかった
Te-form	口くちがうまくて	口くちがうまくなくて
Adverbial	口くちがうまく
Conditional	口くちがうまければ	口くちがうまくなければ
Tara conditional	口くちがうまかったら	口くちがうまくなかったら

Meanings

Describes someone who speaks in a flattering, persuasive, or superficially charming way, often with a negative connotation of insincerity.

舌した先さき三さん寸ずん
舌先三寸 describes empty, insincere flattery meant to deceive, while 口がうまい more broadly describes someone who is naturally smooth-talking or persuasive.
調ちょう子しがいい
調子がいい describes someone who says whatever pleases the listener in the moment, whereas 口がうまい focuses on the skill of talking smoothly and persuasively.

口下手くちべた
口下手 describes someone who is poor at speaking or expressing themselves, the opposite of being 口がうまい.

口くちが軽かるいN3
口が軽い means someone talks too much or can't keep secrets, which learners can confuse with 口がうまい, meaning smooth or flattering speech.

口くちがうまい
Most common spelling; uses kana for うまい to avoid kanji ambiguity.
口くちが上手うまい
Kanji spelling for うまい; less common but still used.
口くちが巧うまい
Rare kanji variant; 巧い can imply skillful, but this spelling is seldom seen.

Compound of 口 (mouth) + が (subject marker) + うまい (skillful, good). Literally 'mouth is skillful', used idiomatically to describe a smooth talker.