Synonyms:
* Glitter: This word suggests a bright, sparkling light.
* Sparkle: Similar to glitter, this implies a bright, flashing light.
* Shimmer: This emphasizes a soft, gentle light.
* Flicker: This implies a rapid, unsteady light.
* Glimmer: A faint, unsteady light.
* Blink: A quick, intermittent light.
* Flash: A sudden, bright burst of light.
* Beam: A steady, bright light.
Antonyms:
* Dim: The opposite of bright and sparkling.
* Dull: Lacking brightness or brilliance.
* Steady: The opposite of flickering or blinking.
* Unwavering: A constant, unchanging light.
The best synonym or antonym for "twinkle" will depend on the specific context in which you are using it.