Definition of saltpeter in US English:

saltpeter

(British saltpetre)

noun

  • another term for potassium nitrate
    • ‘Southwark, on the south bank of the Thames, was the dumping ground for noxious industries like tanning and brewing and dangerous trades like burning lime and making saltpeter.’
    • ‘Potassium nitrate, also known as niter or saltpeter, has been used to preserve meat and is found in toothpaste formulated for sensitive teeth.’
    • ‘Glauber created a mixture of saltpeter, lime, phosphoric acid, nitrogen and potash which was the first completely mineral fertilizer.’
    • ‘The salt most used is common salt, sodium chloride, but saltpetre (which consists of potassium nitrate and sodium nitrate) has similar effects.’
    • ‘The leachate was collected and then chemically converted to true saltpeter, potassium nitrate, by mixing it with a solution of potash.’

Origin

Late Middle English: from Old French salpetre, from medieval Latin salpetra, probably representing sal petrae ‘salt of rock’ (i.e. found as an encrustation). The change in the first element was due to association with salt.

Pronunciation

saltpeter

/sôltˈpēdər//sɔltˈpidər/