AD adjective 1adverb 1noun 9forms 1 adjective1 •Initialism of antidumping. adverb1 •Initialism of Anno Domini (borrowed from Latin); in the year of our Lord.They had a vibrant culture from the 3rd century BC to the 2nd century AD.Today is 4 September AD 2026. noun9 •Initialism of Alzheimer's disease.Many neurodegenerative diseases, including Alzheimer's disease (AD), involve pathological protein deposits. — 2015 •Initialism of assistant director.A few moments later, the A.D. reappears. "They need you," she says. "And could you stop by Wardrobe?" Shannen rolls her eyes. "O.K.!" she snaps. — 1993 •Initialism of air defence or air defense. •Initialism of antidepressant. •Abbreviation of audio description. •Initialism of atopic dermatitis. •Initialism of airworthiness directive. •(Internet) Initialism of after dark. •(US, Navy) Initialism of auxiliary destroyer (a naval tender, a destroyer tender that tends to destroyers). formsADs