Noah Webster's Dictionary (adv.) In an instinctive manner; by force of instinct; by natural impulse.

Multi-Version Concordance Instinctively (2 Occurrences) Romans 2:14 For when Gentiles who have no Law obey by natural instinct the commands of the Law, they, without having a Law, are a Law to themselves; (See NAS) Jude 1:10 Yet these men are abusive in matters of which they know nothing, and in things which, like the brutes, they understand instinctively--in all these they corrupt themselves. (WEY)