British & Australian, informal if someone is po-faced, they look very serious and unfriendly.
The po-faced librarian refused to let me in without my card.Why does she always look so po-faced?
po-faced
adjective having an impassive expression. Influenced by POKER FACE, but most likely to derive from PO (a chamber pot) or 'poh!' (an old exclamation of rejection) UK, 1934
po-faced
Having an overly stern, disapproving, and humorless demeanor. Primarily heard in UK. The film works because it isn't po-faced about it. Instead, it uses humour to great effect in highlighting just how multifaceted the difficult topic can be.I'll never forget our bizarre school dances, with dozens of hormone-frenzied teens under the watchful eyes of po-faced priests.