<p><strong>Noun:</strong></p><ul><li>Plural: phosphori.</li><li>Chemistry: a solid, nonmetallic element existing in at least three allotropic forms:<ul><li>One that is yellow, poisonous, flammable, and luminous in the dark.</li><li>One that is red, less poisonous, and less flammable.</li><li>One that is black, insoluble in most solvents, and the least flammable.</li></ul></li><li>Used in forming smoke screens, its compounds are used in matches and phosphate fertilizers, and it is a necessary constituent of plant and animal life in bones, nerves, and embryos.</li><li>Symbol: P; Atomic weight: 30.974; Atomic number: 15.</li><li>An artificial fly used in angling, resembling this insect.</li></ul>