adjective
1.
prompted by natural instinct or propensity
was quite unable to control her instinctive fear of snakes
Synonyms: instinctual, intuitive, visceral
Related Word: congenital, inborn, innate; ingrained, inherent, intrinsic; natural
Antonyms: reasoned
2.
Synonyms: spontaneous , automatic, impulsive, involuntary, unmeditated, unpremeditated, unprompted, will-less
Related Word: natural, normal, regular, typical
Antonyms: intentional