a measure of a person's intelligence as indicated by an intelligence test; the ratio of a person's mental age to their chronological age (multiplied by 100)
the quality of lacking any predictable order or plan
(thermodynamics) a thermodynamic quantity representing the amount of energy in a system that is no longer available for doing mechanical work; "entropy increases as matter and energy in the universe degrade to an ultimate state of inert uniformity"
doing something in opposition to another way of doing it that you don't like; "his style of painting was a reaction against cubism"
a bodily process occurring due to the effect of some foregoing stimulus or agent; "a bad reaction to the medicine"; "his responses have slowed with age"
an idea evoked by some experience; "his reaction to the news was to start planning what to do"
extreme conservatism in political or social matters; "the forces of reaction carried the election"
a response that reveals a person's feelings or attitude; "he was pleased by the audience's reaction to his performance"; "John feared his mother's reaction when she saw the broken lamp"
(mechanics) the equal and opposite force that is produced when any force is applied to a body; "every action has an equal and opposite reaction"
any act of molesting or interrupting or hindering or disquieting or agitating or arousing from a state of repose or otherwise depriving inhabitants of the peace and quiet to which they are entitled
(physiology) metabolic equilibrium actively maintained by several complex biological mechanisms that operate via the autonomic nervous system to offset disrupting changes