ATTO- Meaning of ATTO- in English atto- BrE AmE ¦æt əʊ AmE ¦æt̬ oʊ▷ — attogram ˈæt əʊ ɡræm AmE ˈæt̬ oʊ- Longman Pronunciation English Dictionary. Английский словарь произношений Longman. 2012