sourpuss
/ˈsaʊərˌpʊs/
noun
- A person who is always complaining, in a bad mood, or looks unhappy.
- My uncle is a real sourpuss; he never smiles at family gatherings.
- Don't be such a sourpuss — it's a beautiful day!
- The grumpy cashier was a sourpuss who made everyone feel unwelcome.