R's, r's1) N-VAR R is the eighteenth letter of the English alphabet.→ See also three Rs2) N-TITLE: n N R is a written abbreviation meaning king or queen. R is short for the Latin words `rex' and `regina'.
...Elizabeth R.3) R is used as an abbreviation for words beginning with r. For example, it is used on maps as a written abbreviation for `river'.4) In the United States, some cinema films are marked R to show that children under 17 years old are only allowed to see them if an adult is with them.
English dictionary. 2008.