1. Happening or arising without apparent external cause
   "spontaneous laughter"; "spontaneous combustion"; "a spontaneous abortion"
   - self-generated 
2. Said or done without having been planned or written in advance
   - ad-lib, unwritten

See also: gut, impulsive, instinctive, instinctual, intuitive, natural, spontaneity, spontaneously, unprompted, unscripted

Antonym: induced

Encyclopedia: Spontaneous

• pronominal
• pronominal phrase
• pronoun
• pronounce
• pronounceable
• pronounced
• pronouncement
• pronto
• pronucleus
• pronunciamento
• pronunciation
• proof
• proof spirit
• proofed
• proofread
• proofreader
• prop
• prop root
• prop up
• prop-leg
• propaedeutic
• propaedeutics
• propaganda
• propagandise
• propagandism