A regular or characteristic response to a stimulation of the nerves.

A counterforce imparted to a speaker enclosure in response to the air resistance to the motion of a moving diaphragm or cone. On a thick carpet, a reacting enclosure will rock slightly back and forth, impairing LF quality and overall detail. See "spike."

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"

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"

a form of panic, gross or subtle, an unconscious response coming from a habit pattern (samskara if you like Sanskrit)

an extension or a response to the repair

a physical response based on what we practiced

a response to something which you perceive as negative

visible response to foreign substance or infection.

A person's voluntary or involuntary response to a hazard or other situation that has been perceived; the response to a sensory stimulus.  Reactions may be reflex, simple, complex, or discriminatory.