O

Universal Words noun, exclamation noun (also o) (plural O's, o's ) 1 [C,U] the 15th letter of the English alphabet: 'Orange' begins with (an) O / 'O'. 2 (spoken) used to mean 'zero' when saying telephone numbers, etc: My number is six o double three (= 6033). seealsoOGRADE, OLEVEL exclamation (rare, especially literary) = OH