Revelation 10:3

This onomatopoetic word (a word which phonetically imitates or resembles the sound that it describes) was never translated honestly in any translation that we have found. See various parallels on the verse for yourself. The translation of "roar" is simply false. 

The "reputed" Thayer's Greek Lexicon even admits the real meaning, and yet still cheats it:

μυκάομαι, μυκωμαι; (from μύ or μύ, the sound which a cow utters (Latinmugio)), to low, bellow, properly, of horned cattle (Homer, Aeschylus, Euripides, Plato, others); to roar, of a lion, Revelation 10:3.

The Abbott-Smith Greek Lexicon of the New Testament falsely represents it as well:

prop., of oxen (onomatop.), to low, bellow; of a lion, to roar: Re 10:3