Pronunciation (US) IPA (key): /ˈætɔl/ or /ˈætɑl/ or /ˈætoʊl/ or /ˈeɪtɑl/ (UK) IPA (key): /ˈætɒl/ or /əˈtɒl/ Noun Singular atoll Plural atolls An atoll is a reef or island that is made of coral. There are many atolls in the Pacific. Wikiwand - on Seamless Wikipedia browsing. On steroids.Remove ads