(espionage) A spy who pretends to work for one side, when they are actually working for or passing information to the other.

Incomprehensible language. / A language game akin to pig Latin. / A game of jump rope with two ropes and frequently two jumpers.

A cousin who is related on both sides of a family. A relative with four common grandparents.

Alternative form of double-u / something in the shape of two U's (not of a W)

(computing) The action of pushing the button on a mouse twice in quick succession in order to perform a different task that would be performed from a single-click or triple-click.

(computing) To push the button on a mouse twice in quick succession in order to perform a different task than would be performed from a single-click or triple-click.

(basketball) A violation committed by dribbling for a second time without giving up possession of the ball.

(physical chemistry) A covalent bond in which two electron pairs (instead of the usual one) are shared between two atoms; most common between carbon atoms and carbon, oxygen or nitrogen atoms, but several other forms are known.

An extra check or verification made a second time, usually with additional caution or attention. / (chess, uncountable) A check delivered by two pieces simultaneously.

To check again; to check with extra caution or attention; to verify or make sure.