This appears to be a compound or archaic term possibly combining borasque (wind) and borate (chemical compound), though usage is unclear.
If this is a genuine term, it would be a 19th-century scientific or linguistic construction combining the wind term with the chemical term—likely obsolete.
This word might be a typo or a ghost word in dictionaries—it's a great reminder that not every word you find in old texts was actually used by regular speakers!
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