hydrogen bromide

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. An irritating colorless gas, HBr, used in the manufacture of barbiturates and synthetic hormones.

Wiktionary

1. n. inorganic chemistry A colourless gas having an irritating smell; it has the molecular formula HBr, and dissolves in water to form hydrobromic acid; it has many industrial applications including the production of barbiturates and synthetic hormones.

WordNet 3.0

1. n. a colorless gas that yields hydrobromic acid in solution with water