reflectron🔊nounUK /ɹɪˈflɛkˌtɹɒn/ · US /ɹɪˈflɛkˌtɹɑn/Etymology From reflect + -tron.1Chemistry, Natural sciences, Physical sciences, Physics A time-of-flight mass spectrometer that uses a static electric field to reverse the direction of travel of the ions entering it.