Mercury (noun)

1. A heavy silvery-white toxic element, the only metal that is liquid at room temperature.
2. A chemical element with the symbol Hg and atomic number 80.
3. A toxic heavy metal that can cause serious health problems.

Origin:

Late middle english: via old french from latin mercurius, from merx, merc- "merchandise", probably because it was used in trade.

Examples:

1. Mercury is used in thermometers.
2. Mercury is a toxic element.
3. The mercury in the thermometer rose.
4. Mercury is a naturally-occurring element.
5. Mercury is present in some types of fish.