diatom UK /ˈdaɪ.ə.təm/US /ˈdaɪ.əˌtɔm/noun 1/daɪˈæ.təm/ noun 1forms 1 noun1 •Any of a group of minute unicellular algae having a siliceous covering of great delicacy, now categorized as class Diatomophyceae or division Bacillariophyta.Diatoms are enclosed in two shells that fit together like a pillbox. — 1967 diatom /daɪˈæ.təm/ noun1 •A molecule composed of two atoms of the same element; a homonuclear diatomic molecule. formsdiatoms
