spontaneous
adjective
1. happening or arising without apparent external cause
- spontaneous laughter
- spontaneous combustion
- a spontaneous abortion
Similar word(s): impulsive, unprompted, intuitive, instinctive, natural
2. said or done without having been planned or written in advance
Similar word(s): unscripted, unwritten
Sentences with spontaneous as an adjective:
- He made a spontaneous offer of help.
- a spontaneous growth of wood