As a Noun: 1. A very strong feeling of anxiety or fear, especially one that makes you act without thinking carefully. English = panic. As a Verb or Adjective: 1. To act without thinking carefully because you are very anxious or frightened. English = panic. 2. To react without thinking or with confusion to a situation because you are unprepared or surprised by it. Idiomatic English = (be) off one's guard, (be) caught unawares.