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.