po-faced /ˌpəʊ ˈfeɪst◂ $ ˌpoʊ-/ BrE AmE adjective British English informal
[ Date: 1900-2000 ; Origin: Perhaps from po 'chamber pot' (19-20 centuries) , from French pot , influenced by poker-faced ]
having an unfriendly disapproving expression on your face SYN stern