As a Noun: 1. A fluttering and nauseated feeling in the stomach when you feel nervous. English = nervousness, anxiety. Idomatic English = butterflies in your stomach. As a Verb or Adjective: 1. To have a fluttering and nauseated feeling in the stomach because you feel nervous. English = (be) nervous, (be) anxious. Idomatic English = have butterflies in your stomach.