A submariner on a U-boat

(linguistics) The form of Received Pronunciation used by the upper classes.

(proofreading) Initialism of upper-case.

A rental vehicle, especially a moving truck.

(calculus) A method of integration in which a function of a variable is replaced with a new variable, conventionally called u.

(UK, education) A school-leaving qualification that is an alternative to A levels.

(linguistics) The sound /juː/, as in the words "cube" and "mute".

(linguistics) The vowel sound, /ʌ/, in the words "cut" and "run".

plural of U-value

A person or vehicle that performs a U-turn. / Someone who shifts from a previously held opinion or decision to its opposite.