element zero
nounEtymology From being a chemical element with zero protons.
1
Literature, Media, Publishing, Science fiction Informal Synonym of neutronium (“material composed of neutrons”).
Nuclear physics
2
Informal Synonym of muonium.
Nuclear chemistry
3
Literature, Media, Publishing, Science fiction A fictional chemical element with element number/atomic number/proton number zero (0), often with unrealistic properties.
4
Used other than figuratively or idiomatically: see element, zero.