A colorless poisonous corrosive liquid made by the action of sulphuric acid on calcium fluoride; solutions in water are hydrofluoric acid WordNet 3.0 & Open English WordNet

Hydrogen fluoride is an inorganic compound with chemical formula HF. Wikipedia

HF, a diatomic compound which can dissolve in water to form hydrofluoric acid, a highly corrosive solution Wikipedia Disambiguation

A colourless fuming liquid or gas, having a molecular formula of HF; it dissolves in water to form hydrofluoric acid and has many industrial uses including the production of Teflon and the refining of uranium; it corrodes skin, flesh and bone, and any skin contact must be avoided. Wiktionary

HF. Wiktionary (translation)