/ˈhi:liəm ||; ˈhilɪəm/noun [U] (symbol He) a very light colourless gas that does not burn, often used to fill objects that float in the air(balloons) 氦（一种质轻、无色的气体，常用于充气球） Helium is a noble gas. 氦是一种惰性气体(noble gas)。