spontaneous

US /spɑːnˈteɪ.ni.əs/
UK /spɑːnˈteɪ.ni.əs/
1.

spontan

performed or occurring as a result of a sudden inner impulse or inclination and without premeditation or external stimulus.

:
•
the audience broke into spontaneous applause
:
unforcedvoluntaryunconstrainedunpromptedunbiddenunsolicitedunplannedunpremeditatedunrehearsedimpulsiveimpetuousunstudiedimpromptuspur-of-the-momentextemporeextemporaneousunschooleduntaughtuninstructedoff-the-cuff
:
plannedforcedcalculated