fluttering

Etymology

noun

1. Rapid back-and-forth waving or oscillation.
   It is indubitably certain, therefore, that he is able to attend, and actually attends, to all things at the same moment; to the motions of a seed, or a leaf, or an atom; to the creepings of a worm, the flutterings of an insect, and the journeys of a mite […] 1824, Timothy Dwight, Theology, Explained and Defended in a Series of Sermons
   Miss Greta closed her eyes. Quickly, however, did she open them again; for a dull noise, with certain whiskings-about and flutterings, together with low clatterings, approached her ear. 1844, Fredrika Bremer, The Neighbours: A Story of Every-day Life, page 59

verb

1. present participle and gerund of flutter