re·flex 
/ˈri:ˌflɛks/ noun
plural re·flex·es /ˈri:ˌflɛks/ noun 1 [count] : an action or movement of the body that happens automatically as a reaction to something
▪ the cough/gag reflex ▪ reflexes such as swallowing and blinking ▪ a reflex action/response 2 [count] : something that you do without thinking as a reaction to something
▪ Disagreeing with my suggestions has become almost a reflex for him. 3 reflexes [plural] : the natural ability to react quickly
▪ an athlete with great/quick reflexes ▪ My reflexes are slower now that I'm older.
▪ the cough/gag reflex ▪ reflexes such as swallowing and blinking ▪ a reflex action/response
▪ Disagreeing with my suggestions has become almost a reflex for him.
▪ an athlete with great/quick reflexes ▪ My reflexes are slower now that I'm older.
