phosphamChem.|ˈfɒsfæm| [f. phosph- + ammonia).] The nitril of phosphoric acid (PHN2); a white, reddish, or yellowish-red powder. 1866–77Watts Dict.Chem. IV. 497 Phospham..is a bulky powder, white if moisture has been carefully excluded during its preparation, reddish in the contrary case.