noun
curmudgeon
ker-MUJ-un/kɜːrˈmʌdʒən/
A grumpy, bad-tempered person, usually older.
Our neighbor is a curmudgeon who complains about everything.

Etymology
The word’s origin is unknown. Its earlier use for a churlish, miserly fellow connects with today’s bad-tempered person through an enduring sense of disagreeableness.
In context
I am a complete curmudgeon about this movie. I'm totally negative about it.
More examples
- Even that old curmudgeon smiles when his granddaughter visits.
- I'm a bit of a curmudgeon before my morning coffee.
- The two curmudgeons grumble about the music throughout dinner.
Forms
curmudgeon · curmudgeons
curmudgeonly adjective — Grumpy and inclined to complain.
Similar words
- grouch
- A more casual term, without suggesting an older person.
- crank
- Can suggest odd opinions as well as an irritable temperament.