(nautical) The practice of having two alternate watches aboard a ship or vessel.

having exactly two arms

(Cockney rhyming slang) A state (of upset, worry).

(mathematics) A measure of length given by "the square root of the squares." Denoted by ||·||₂, the two-norm of a vector ⃑v= is ||⃑v||₂=√. The two norm of an m⨯m matrix A is defined by max _(⃑v≠⃑0)|/} where ⃑v is an m-dimensional vector that is not the zero vector.

(computing) The number obtained by complementing every bit of a given number and adding one. A number and its complement add to 2ⁿ, where n is the word size of the machine.

Existing in two dimensions. / Not creating the illusion of depth; lacking detail or believability.

Forty plus two; the cardinal number following forty-one and preceding forty-three.

(Australia, New Zealand, games) A game of chance, played by betting on the outcome of two pennies thrown in the air.

(of a printed document) Having two document pages per printed page.

(manner, of travel on a motorcycle) With two people aboard.