smart–mouth or smart–mouthed 
/ˈsmɑɚtˌmaʊθ/ /ˈsmɑɚtˌmaʊθt/ adjective
/ˈsmɑɚtˌmaʊθ/ /ˈsmɑɚtˌmaʊθt/ adjective US, informal + disapproving : saying rude or disrepectful things
▪ smart-mouth comments ▪ a bunch of smart-mouthed kids
▪ smart-mouth comments ▪ a bunch of smart-mouthed kids
— smart–mouth noun, plural smart–mouths [count]
▪ He's a real smart-mouth.
▪ He's a real smart-mouth.
