helium
nounUK /ˈhiːliəm/
US /ˈhiːliəm/
Helium is a very light gas that makes balloons float up in the air.
We filled the birthday balloons with helium so they would float.
SYNONYMS
OTHER MEANINGS
2. A chemical element with the symbol He and atomic number 2, the second lightest element.
Helium is the second most abundant element in the universe.
3. A colorless, odorless, nonflammable gas used in cryogenics and breathing mixtures.
Divers use a helium-oxygen mixture to breathe at great depths.
4. A gas used to cool superconducting magnets in MRI machines.
The hospital needs liquid helium to keep its MRI scanner cold.