Surface defects, depressions, or irregular marks left on a machined part when a cutting tool vibrates, deflects, or is pushed too hard against the material. These blemishes ruin the surface finish and often mean the part fails inspection. They are usually caused by a lack of rigidity in the setup or incorrect cutting parameters.
Back off the feed rate a bit, you're leaving utters all over that face.
If you see utters forming, immediately check your tool overhang and make sure the workpiece is clamped tightly.
Related terms
Chatter
Self-sustaining vibration between tool and work that screams, leaves a wavy pattern and kills tools.
Chattermark
A visible pattern of ripples or lines left on a machined surface due to tool vibration.
Rubbing
A tool sliding over the work without taking a proper chip, usually because the feed is too light or the tool is dull.