See also: atra, atrá, ātra, ātrā, and -atra English Noun ATRA (uncountable) (organic chemistry, pharmacology) Initialism of all-trans retinoic acid. Anagrams ta-ra, taar, Tārā, Arta, Tara, tara, A.A.R.T., rata, Atar, atarWikiwand - on Seamless Wikipedia browsing. On steroids.Remove ads