moan or complain about somebody or something
grumble - complain
When a person ‘grumbles’, they complain about usually trivial things in a continuous and irritating way, which can be annoying for those forced to listen to it. Grumbling is often a pointless, self-indulgent act, and can negatively affect morale within a group.
Kate likes to grumble that her job isn’t challenging enough for her, yet she struggles anytime she’s given any responsibility.
Oh, please stop grumbling! You’ve been banging on about the weather all day!
Person A: “I’m surprised Tom didn’t complain about the delay.” Person B: “Oh, he did. He grumbled about it incessantly.”