1. DDO - Noun
2. DDO - Proper noun
Initialism of David Dunlap Observatory.
Initialism of Dollard-des-Ormeaux (municipality in the province of Quebec, Canada.)
DDO (plural DDOs)
(software) Initialism of dynamic drive overlay (a type of computer software; a form of driver)
Examples for Dungeons and Dragons Online include "Tolero" (who hosted a long running role play segment on the unofficial DDO podcast, DDOcast), and Jerry Snook (creator and host of said cast). Source: Internet