Origin: Cf. F. Spontaneite.
1. The quality or state of being spontaneous, or acting from native feeling, proneness, or temperament, without constraint or external force. Romney Leigh, who lives by diagrams, And crosses not the spontaneities Of all his individual, personal life With formal universals. (Mrs. Browning)
2. (Science: biology) The tendency to undergo change, characteristic of both animal and vegetable organisms, and not restrained or cheked by the environment. The tendency to activity of muscular tissue, including the voluntary muscles, when in a state of healthful vigor and refreshment.