Source : Webster's Revised Unabridged Dictionary (1913)

Cottonwood \Cot"ton*wood`\ (-w[oo^]d`), n. (Bot.)
   An American tree of the genus {Populus} or poplar, having the
   seeds covered with abundant cottonlike hairs; esp., the {P.
   monilifera} and {P. angustifolia} of the Western United
   States.