adjective

showing a lack of respect or politeness in a way that is amusing or appealing.

a cheeky grin

impudent,impertinent,insolent,presumptuous,forward,pert,bold,bold as brass,brazen,brazen-faced,shameless,audacious,overfamiliar,irreverent,discourteous,disrespectful,insubordinate,impolite,bad-mannered,ill-mannered,unmannerly,mannerless,rude,insulting,brass-necked,cocky,lippy,mouthy,fresh,flip,saucy,smart-arsed,sassy,nervy,smart-assed,malapert,contumelious,presumptive,assumptive