Being the size of a twin bed.

Either of a pair of matching single beds. / (US) A single bed.

(idiomatic) A duplicate or counterpart that acts in a contrary, nefarious, or insidious manner.

(rare, slang, offensive) Either of a pair of siblings born less than 12 months apart, especially if born within the same calendar year or school year or born one year apart.

(relativity) The clock paradox.

(mathematics) Either of a pair of prime numbers that differ by two.

One of exactly two siblings produced from the splitting of a single zygote.

Alternative form of twincam

plural of twin quasar

(astronomy) a pair of quasar images formed by gravitational lensing of a single physical quasar