atrial septal defect atrial fibrillation • atrichia · · · Info · Definitions · Characters · · atrial septal defect · · Text Common · · Latin · · Scripts 20 · · Length 6 · · Syllables Definitions · · · (noun) an abnormal opening between the left and right atria of the heart. Synonyms: atrial septal defect. · · Noun Definition 1 Characters · · space U+0020 a latin small letter a U+0061 c latin small letter c U+0063 d latin small letter d U+0064 e latin small letter e U+0065 f latin small letter f U+0066 i latin small letter i U+0069 l latin small letter l U+006C p latin small letter p U+0070 r latin small letter r U+0072 s latin small letter s U+0073 t latin small letter t U+0074