The noun 嘴巴 (zuǐba) means 'mouth.' It is the colloquial, everyday form compared to the more concise 嘴 or the formal 口. The suffix 巴 softens the word and makes it more conversational. It is commonly used when referring to the physical mouth on a person's face.
他嘴巴张得大大的,一脸惊讶。
Tā zuǐba zhāng de dà dà de, yì liǎn jīngyà.
His mouth was wide open, with a look of surprise on his face.
小孩子嘴巴甜,谁都喜欢他。
Xiǎo háizi zuǐba tián, shéi dōu xǐhuan tā.
The little kid has a sweet mouth; everyone likes him.
你嘴巴上都是巧克力,快擦擦。
Nǐ zuǐba shàng dōu shì qiǎokèlì, kuài cā cā.
You have chocolate all over your mouth; wipe it off quickly.