- Proper noun. (Greek mythology) One of the Dioscuri.
- Proper noun. (star) A double star in the constellation Gemini; alpha (α) Geminorum.
- Noun. A pivoting roller attached to the bottom of furniture to allow it to be moved.
- Noun. A hat made from the fur of the beaver.
- Noun. A caster; a container with perforated cap for sprinkling (e.g. ''pepper-castor'').