|Origin:||, past participle of reflectere; REFLECT|
the natural ability to react quickly and well to sudden situations
have good/quick/slow reflexes
A tennis player needs to have very quick reflexes.
a sudden uncontrolled movement that your muscles make as a natural reaction to a physical effect:
Doctor Mulholland tested Jennifer's reflexes (=especially by hitting her knee with a special rubber hammer).
something that you do without thinking, as a reaction to a situation