1 : to make a light less bright or to become less bright

[+ object]

• Dim the lights.
• The car’s headlights were dimmed.

[no object]

• The lights dimmed.

2 : to make something less strong or clear or to become less strong or clear

[+ object]

• The latest setback has dimmed hopes of an early settlement.

[no object]

• Hopes of an early settlement have dimmed.
• Her beauty dimmed rapidly.