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acromegaly a chronic disease causing abnormal enlargement of the hands, feet, and parts of the face, usu. caused by a tumor of the pituitary gland.
acronym a type of abbreviation used as a word, formed by combining the initial letters (or initial parts) of words that make up a particular string. The pronunciation of an acronym is based on the typical rules of pronouncing words in a language and is not made up of the sounds of the names of individual letters.
acrophobia an overwhelming fear of high places.
acropolis a fortified hill of an ancient Greek city. [2 definitions]
across from one side or end to the other of. [7 definitions]
across the board applying equally to all parts or members.
acrostic a sequence of written lines in which particular letters, usu. the first letter of every line, form an independent word or phrase. [2 definitions]
acrylic of or characteristic of the corrosive liquid, acrylic acid. [2 definitions]
acrylic fiber any of a group of synthetic fibers that are made chiefly of acrylonitrile that has been formed into polymers.
acrylic resin any of a group of transparent synthetic resins that become pliable or set when heated and are used in acrylic fibers, plastics, and synthetic rubbers.
acrylonitrile a poisonous and carcinogenic liquid that is made into polymers for use as raw material in acrylic fibers.
act something done, esp. a specific instance; deed. [14 definitions]
actable capable of being acted, as a role or a play.
ACTH a hormone produced by the anterior pituitary that stimulates the cortex of the adrenal gland to produce cortisone and other hormones; adrenocorticotropic hormone.
acting appointed as a temporary substitute for someone absent from an office or position; serving temporarily. [5 definitions]
actinic of or pertaining to the chemical property of ultraviolet radiation and x-rays that produces photochemical effects.
actinic rays electromagnetic radiation, such as x-rays or ultraviolet light, that can produce an image on a photographic emulsion.
actinide any of the chemical elements of the actinide series.
actinide series the series of chemical elements, mostly synthetic and all radioactive, that have from eighty-nine to 103 protons per atom.
actinism the property of radiation that produces chemical activity.
actinium a radioactive chemical element of the rare-earth group that has eighty-nine protons in each nucleus. (symbol: Ac)