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oxycephaly a condition in which the skull is somewhat peaked or conical, as the result of premature closing of the skull sutures.
oxygen a chemical element that has eight protons in each nucleus and that occurs in pure form, as a colorless, odorless gas essential to the respiration of living things, or in important compounds such as water, carbohydrates, and oxide minerals. (symbol: O)
oxygenate to combine, supply, or treat with oxygen.
oxygenless combined form of oxygen.
oxygen tent a transparent, tentlike enclosure that is fitted around the head and shoulders of a bedridden patient to form a chamber into which oxygen can be released.
oxyhydrogen of or pertaining to a mixture of oxygen and hydrogen. [2 definitions]
oxymoron a figure of speech in which an apparent contradiction makes or highlights a point, as in the phrase "a frozen flame".
oxytocin a hormone produced by the pituitary gland that increases contractions of the uterus and stimulates milk production.
oyez hear ye! attention! (usu. called out three times by a court or public official to command silence before an official proclamation is made).
oyster any of various edible mollusks found chiefly in shallow water and characterized by a lumpy, irregular bi-valved shell, esp. the pearl oyster. [3 definitions]
oyster bed a place on the ocean floor where oysters naturally breed or one that is prepared for their cultivation.
oystercatcher any of several black and white shore birds having strong, reddish beaks with which they open and feed on bivalve mollusks such as oysters.
oyster crab a small crab that lives as a commensal inside the gill cavities of living oysters and clams.
oyster cracker a small round soda cracker, usu. eaten with oysters, stews, or soups.
oyster plant see salsify.
oysters Rockefeller broiled oysters served on the half shell topped with spinach, bacon, seasonings, and cream sauce or butter.
oz. abbreviation of "ounce," or "ounces," a unit of weight equal to one sixteenth of a pound or 28.350 grams in the avoirdupois weight system, and equal to one twelfth of a pound or 31.1051 grams in the apothecaries' weight and the troy weight systems.
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 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]