Usually in parentheses: abbreviation of unclassified.
In a film certificate: abbreviation of universal (“suitable for all ages”).
A U-turn ('turned a U in the road')
The twenty-first letter of the English alphabet, called u and written in the Latin script.
A double upright cordon espalier (also double U, triple U).
A U-turn.
A language belonging to the Austroasiatic language family which is spoken in China.
The element with atomic number 92 and symbol U: a radioactive silvery-grey metal in the actinide series.