- a reverse movement or tendency; an action in a reverse direction or manner.
- movement in the direction of political conservatism or extreme rightism.
- action in response to some influence, event, etc.: the nation's reaction to the president's speech.
- action in response to a stimulus, as of the system or of a nerve, muscle, etc.
- Medicine/Medical.
- the action caused by the resistance to another action.
- a return to the opposite physical condition, as after shock, exhaustion, or chill.
- the specific cellular response to foreign matter, as in testing for allergies.
- the reciprocal action of chemical agents upon each other; chemical change.
- a process in which a nucleus that is bombarded by a photon, particle, or other nucleus, emits a nucleon, alpha particle, or the like, without a significant change in its atomic weight.
- the instantaneous response of a system to an applied force, manifested as the exertion of a force equal in magnitude but opposite in direction to the applied force.
- a decline in the market after an advance in prices.
- a response to some foregoing action or stimulus
- the reciprocal action of two things acting together
- opposition to change, esp political change, or a desire to return to a former condition or system
- a response indicating a person's feelings or emotional attitude
- med
- any effect produced by the action of a drug, esp an adverse effect
- any effect produced by a substance (allergen) to which a person is allergic, the simultaneous equal and opposite force that acts on a body whenever it exerts a force on another body
- short for chemical reaction, nuclear reaction
- a sharp fall in price interrupting a general rise
