Emily Dickinson Lexicon

SPON-TA'NE-OUS, a. [L. spontaneus, from sponte, of free will.]

1. Voluntary; proceeding from one's own will, without other cause; applied to persons; as a spontaneous gift or proposition.
2. Acting by its own impulse, energy or natural law, without external force, as spontaneous motion; spontaneous growth; spontaneous combustion.
3. Produced without being planted, or without human labor; as, a spontaneous growth of wood. Spontaneous combustion, a taking fire of itself. Thus oiled canvas, oiled wool, and many other combustible substances, when suffered to remain for some time in a confined state, suddenly take fire, or undergo spontaneous combustion.