2. (Science: neurology, physiology) A reflected action or movement, the sum total of any particular involuntary activity. An automatic instinctive unlearned reaction to a stimulus. (biology-online.org)
3. An action or movement of the body that happens automatically as a reaction to something; something that you do without thinking as a reaction to something (merriam-webster.com)
4.An action consisting of comparatively simple segments of behaviour that usually occur as direct and immediate responses to particular stimuli uniquely correlated with them. (global.britannica.com)
5. a. Something, such as light or heat, that is reflected; b. An image produced by reflection; a copy or reproduction.(thefreedictionary.com)
6. (Psychology) An unlearned or instinctive response to a stimulus.
1. (Of an action) Performed without conscious thought as an automatic response to a stimulus. (Google Dictionary)
2. (Physiology) Being an involuntary action or response, such as a sneeze, blink, or hiccup. (thefreedictionary.com)
Word origin: from Late Latin reflexus “a bending back.”