Synonyms of the word

unprompted

• adj. Not prompted.

impulsive

• adj. Having the power of driving or impelling; giving an impulse; moving; impellent.
• adj. Actuated by impulse or by transient feelings; inclined to make rapid decisions without due consideration.
• adj. (mechanics) Acting momentarily, or by impulse; not continuous – said of forces.
• n. That which impels or gives an impulse; an impelling agent.
• n. One whose behaviour or personality is characterized by being impulsive.

spontaneous

• adj. Self-generated; happening without any apparent external cause.
• adj. Done by one's own free choice, or without planning.
• adj. proceeding from natural feeling or native tendency without external or conscious constraint.
• adj. arising from a momentary impulse.
• adj. controlled and directed internally; self-active; spontaneous movement characteristic of living things.
• adj. produced without being planted or without human labor; indigenous.
• adj. Random.
• adj. Sudden, without warning.