to grumble, to grouse, to complain [verb] [mopperde, gemopperd] [‘mo-pu-run’]

This verb has nothing to do with DWOTD
219. Mop, but is inspired by yesterday’s "
Somebody who "moppers" is called a "mopperaar", but mostly you will
hear "mopperkont", which translates to something like "grumble butt" 🙂

– "Ik word niet goed van opa! De hele dag door niets anders dan mopperen!"
is driving me crazy! All day long nothing but grumbling!" Literally: "I
am becoming not well because of grandpa." The expression "niet goed
worden van" is very common. Without a subject it needs the ever tricky
"er": "Ik word er niet goed van": "It is driving me crazy" or "I have
had it (with it)".)

– "Wat zit je te mopperen? Is het weer niet goed?"
("What are you grumbling about? Is it once again not to your liking?")

– "De chef moppert de hele dag op zijn personeel."
("The manager
grumbles at his personnel all day." The word "chef" is used for
managers in production environments, including supermarkets and such.)

Related words:
– "Mopperkont": grumbler/grouch, somebody who complains a lot.
– "Mopperpot": like "mopperkont" but less common.