noun Chiefly British.
- potassium nitrate.
- sodium nitrate.
- another name for potassium nitrate, sodium nitrate
- the usual US spelling of nitre
n.c.1400, “native sodium carbonate,” from Old French nitre (13c.), from Latin nitrum, from Greek nitron, which is possibly of Eastern origin (cf. Hebrew nether “carbonate of soda;” Egyptian ntr). Originally a word for native soda, but also associated from Middle Ages with saltpeter (potassium nitrate) for obscure reasons; this became the predominant sense by late 16c. see nitre.
- A naturally occurring mineral form of potassium nitrate. It is used to make gunpowder.