From Longman Dictionary of Contemporary EnglishDD, d /diː/ (plural D’s, d’s) noun 1 [countable, uncountable]SLA the fourth letter of the English alphabet2 [countable, uncountable]APM the second note in the musical scale of C major or the musical key based on this note3 [countable]SE a mark given to a student’s work to show that it is not very good I got a D in history last semester.4 HMNthe number 500 in the system of roman numerals → D and C
Examples from the Corpus
D• Abraham Lincoln, for example, was a D & B credit reporter.d.d. (also d British English)1 DIEthe written abbreviation of died John Keats d. 18212 PECthe written abbreviation of penny or pence in the system of money used in Britain before 1971d'd' /d/DOthe short form of ‘do’ D'you know how many people are going to be there?From Longman Business DictionaryddFINANCE written abbreviation for DIVIDEND 