Definitions of flutter:

• noun:   abnormally rapid beating of the auricles of the heart (especially in a regular rhythm); can result in heart block
• noun:   the act of moving back and forth
• noun:   the motion made by flapping up and down
• noun:   a disorderly outburst or tumult
• verb:   wink briefly
• verb:   beat rapidly
• verb:   move along rapidly and lightly; skim or dart
• verb:   move back and forth very rapidly