nitrate(1) A salt of nitric acid, or compound containing the radical NO3. (2) Nitration n. acidium* See nitracidium ion. n. ion The NO3- ion colorless, and forming no, insoluble precipitates with metallic ions. n. of lime Calcium n. n. of potash Potassium n. n. of soda sodium n, n. of soda potash A crude Chilean saltpete: sodium nitrate 75, potassium nitrate 25% a fertilizer.