HBr

from The Collaborative International Dictionary of English v.0.48

Hydrobromic \Hy`dro*bro"mic\, a. [Hydro-, 2 + bromic.] (Chem.)
   Composed of hydrogen and bromine; as, hydrobromic acid.
   [1913 Webster]

   {Hydrobromic acid} (Chem.), a colorless, pungent, corrosive
      gas, {HBr}, usually collected as a solution in water. It
      resembles hydrochloric acid, but is weaker and less
      stable. Called also {hydrogen bromide}.
      [1913 Webster]