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ozone oxygen in the form of molecules with three atoms, created by exposure of oxygen to electrical discharge or ultraviolet radiation, having a sharp smell, and being an effective oxidant for use in bleaching and sterilizing.
ozone depletion a steady decline in ozone in Earth's stratosphere, or a springtime decline in stratospheric ozone in Earth's polar regions. The primary cause of ozone depletion is man-made chemicals, particularly chlorofluorocarbons (CFCs).
ozone hole an area in the ozone layer where the ozone becomes thin. There is a large ozone hole over Antarctica and a smaller one over the North Pole. Scientists warn us this is dangerous.
ozone layer an atmospheric layer between ten and twenty miles above the earth that contains a substantial concentration of ozone, which absorbs ultraviolet radiation from space and prevents some heat loss from the earth; ozonosphere.
ozonize to treat, combine, or saturate with ozone. [2 definitions]
ozonosphere see ozone layer.
P1 abbreviation of "passing," completed successfully.
P2 symbol of the chemical element phosphorus.
P- in the U.S. military, a pursuit plane, such as a P-38 or P-40.
p the sixteenth letter of the English alphabet. [3 definitions]
p. abbreviation of "page," one side of a sheet of printed or written paper. [2 definitions]
PA1 abbreviation of "Pennsylvania," an eastern U.S. state south of New York.
Pa symbol of the chemical element protactinium.
PA2 abbreviation of "public address."
pa (informal) father; papa.
pa'anga the chief monetary unit of Tonga, equaling one hundred seniti.
Pablo Picasso a Spanish painter and sculptor (b.1881--d.1973).
Pablum trademark for a smooth, bland baby cereal. [2 definitions]
pabulum a soft substance that serves to nourish. [2 definitions]
PAC abbreviation of "political action committee."
pac an insulated, waterproof boot designed for wear in extreme cold. [3 definitions]