impish
adjective /ˈɪmpɪʃ/
  /ˈɪmpɪʃ/
- showing a lack of respect for somebody/something in a way that is funny rather than serious synonym mischievous
- an impish grin/look
 - He takes an impish delight in shocking the press.
 
Oxford Collocations DictionaryImpish is used with these nouns:- grin