From Longman Dictionary of Contemporary EnglishLetters & punctuationUU1, u /juː/ (plural U’s, u’s) noun    1 [countable, uncountable]SLA the 21st letter of the English alphabet2 [singular, uncountable] British English used to describe a film that has been officially approved as suitable for people of any age SYN G American English3 [countable] British English a mark given to a student’s work to show that it is extremely bad → U-boat, U-turnExamples from the CorpusU• Then, from U, some one else sets off for Lamri and for Lorpa.• Some one hears it mentioned in the Bazaar and runs to U with a warning.UU2 pronoun written informal    a way of writing ‘you’, used especially in emails and text messages  I love U!CollegeU.U., U /juː/    American English informalSEC an abbreviation of university  Indiana U