adverb
reflexively; by reflex; automatically
Describes an action done without conscious thought, as an automatic reaction.
ボールが飛んできたので、反射的に手で顔をかばった。
When the ball came flying, I reflexively covered my face with my hands.
彼は質問されると、反射的に「いいえ」と答える癖がある。
He has a habit of reflexively answering 'no' when asked a question.
無意識に also means 'unconsciously', but 反射的に emphasizes an automatic physical or mental reaction, while 無意識に can refer to any unconscious action.
Derived from 反射 (reflex) + 的 (adjective-forming suffix) + に (adverbial suffix).