To fret, chomp, or show restless irritation, especially of a horse chomping its bit.
Possibly from Old French or Germanic origins, related to 'franch' meaning to thrust forward. The term particularly developed in equestrian vocabulary to describe a horse's anxious behavior.
This wonderfully onomatopoetic word captures exactly the sound and behavior of a horse nervous and eager to go—you can almost hear the crunching of the bit when you say 'fraunch,' which is why horsemen have used this term for centuries.
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