Xenon-based lifeform

From Memory Alpha, the free Star Trek reference

A xenon-based lifeform is a corporeal lifeform which uses xenon as the basis of its structure and life functions rather than carbon.

In 2374, Neelix was attempting to conduct trade negotiations with a xenon-based lifeform when his universal translator went off-line. Fortunately, Neelix was saved by Arturis, who was able to step in and serve as a mediator despite never hearing either language prior to that moment. (VOY: "Hope and Fear")