"selenium" in the noun sense
1. selenium, Se, atomic number 34
a toxic nonmetallic element related to sulfur and tellurium occurs in several allotropic forms a stable grey metallike allotrope conducts electricity better in the light than in the dark and is used in photocells occurs in sulfide ores (as pyrite)
Source: WordNet® (An amazing lexical database of English)
Princeton University "About WordNet®."
WordNet®. Princeton University. 2010.
View WordNet® License