Definition of spontaneous:
random, uncontrollable, mechanic, alkaloid, unceremonious, extemporary, mechanical, unforced, accidental, active, plain, unprompted, anaerobic, aerobic, laid-back, self-generated, chemical equation, free, volitional, by accident, alkaline, voluntary, planned, unforced, unrestrained, unplanned, reflex, coincidental, irresistible, unwilling, easy, tighten, natural, instinctive, inevitable, unconscious, impulsive, extempore, automatic, unbidden, offhanded, unwritten, easygoing, willful, robotic, offhand, concentrated, casual, unplanted, unintended, casual, instinctive, chemical, resistless, corrosive, off-the-cuff, willing, unintentional, catalytic, knee-jerk, relaxed, wild, unavoidable, impulsive, instinctual, informal, intuitive, ad-lib, anaerobic, uncompelled, involuntary, unscripted, oral, arbitrary, self-produced.
- friendly (part of speech: adjective)
- impulsive (part of speech: adjective)
- "Ways of Nature", John Burroughs.
- "A Short History of Greek Philosophy", John Marshall.
- "Old Calabria", Norman Douglas.