"helium" in the noun sense
1. helium, He, atomic number 2
a very light colorless element that is one of the six inert gasses the most difficult gas to liquefy occurs in economically extractable amounts in certain natural gases (as those found in Texas and Kansas)
Source: WordNet® (An amazing lexical database of English)
Princeton University "About WordNet®."
WordNet®. Princeton University. 2010.
View WordNet® License