butterflies in stomach
butterflies in (one's) stomach
A feeling of nervousness. The butterflies in my stomach almost kept me from going on stage and performing.
*butterflies in one's stomach
a nervous feeling in one's stomach. (*Typically: get ~; have ~; give someone~.) Whenever I have to speak in public, I get butterflies in my stomach. She always has butterflies in her stomach before a test. It was not frightening enough to give me butterflies in my stomach, but it made me a little apprehensive.