quaking aspen

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A North American deciduous tree (Populus tremuloides) having broadly ovate, finely toothed leaves with a truncate base.

Wiktionary

1. n. Populus tremuloides, the American aspen, so called from its leaves whose flattened petioles cause them to tremble in the breeze.

GNU Webster's 1913

1. (Bot.) an American species of poplar (Populus tremuloides), the leaves of which tremble in the lightest breeze. It much resembles the European aspen. See Aspen.

WordNet 3.0

1. n. Old World aspen with a broad much-branched crown; northwestern Europe and Siberia to North Africa