noun
1. : either of two European birches with white or ash-colored bark:
a. : a birch ( Betula pendula ) with smooth twigs and markedly drooping branches
b. : a birch ( B. pubescens ) with pubescent twigs and somewhat drooping branches
2. : either of two No. American birches with predominantly white bark:
a. : paper birch
b. : american gray birch