Being one of two born at a birth; as, a twin brother or sister.
- One of two offspring born at the same birth.
- One of two identical or similar people, animals, or things; a counterpart.
- Mineralogy Two interwoven crystals that are mirror images of each other.
- A twin-size bed.
- Being two or one of two offspring born at the same birth: twin sisters.
- Being two or one of two identical or similar people, animals, or things: twin cities; a twin bed.
- Botany Of or relating to structures, such as flowers, that occur in pairs.
- Consisting of two identical or similar parts: a twin lamp fixture.
- To give birth to twins.
- Archaic To be one of twin offspring.
- To be paired or coupled.
- To pair or couple.
- To provide a match or counterpart to.