We don't have synonyms for atomic clocks yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are atomic clock.
(n) :
An extremely accurate reference clock whose operation is based on an atomic process, typically the frequency of electromagnetic radiation associated with a specified energy-level transition in an element such as cesium.
(n) :
An extremely accurate reference clock whose operation is based on an atomic process, typically the frequency of electromagnetic radiation associated with a specified energy-level transition in an element such as cesium.