The Collaborative International Dictionary of English v.0.48:

Atoll \A*toll"\, n. [The native name in the Indian Ocean.]
   A coral island or islands, consisting of a belt of coral
   reef, partly submerged, surrounding a central lagoon or
   depression; a lagoon island.
   [1913 Webster]

WordNet (r) 3.0 (2006):

atoll
    n 1: an island consisting of a circular coral reef surrounding a
         lagoon

The Free On-line Dictionary of Computing (19 January 2023):

Acceptance, Test Or Launch Language
ATOLL

    (ATOLL) The language used for automating the
   checking and launch of Saturn rockets.

   ["SLCC ATOLL User's Manual", IBM 70-F11-0001, Huntsville AL
   Dec 1970].

   (2000-04-03)