metal halide lamp

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A lamp in which ultraviolet and visible light is produced by an electric discharge through a mixture of gases containing metal halides at high temperatures and pressures.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A high-pressure discharge lamp that is enclosed in a quartz envelope containing metal halides (usually iodides), and produces high-efficacy white light.