How to say "grumpy" in Japanese

• 愚痴っぽいぐちっぽい
  i-adjectiveCovers grumpy in the querulous sense: a person prone to complaining, who grumbles petulantly about things. It is the less common of the two; a typical context is a colleague who complains about everything.
• 気難しいきむずかしいCommon
  i-adjectiveThe common word for grumpy as a sullen, bad-tempered mood: displeased, in a bad mood, hard to please. Typical context: a boss who is sullen and difficult to deal with today.
  彼女かのじょは気難きむずかしそうに見みえるが、本当ほんとうは優やさしい。↗

  She looks bad-tempered, but she is kind at heart.

Choose 「気難しい」 for grumpy meaning bad-tempered, sullen or in a bad mood, and 「愚痴っぽい」 when the grumpiness amounts to a habit of grumbling and complaining; the latter is the less common word.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

• 愚痴っぽいぐちっぽいprone to complaining
• 気難しいきむずかしいbad-tempered