Still staring into her daughter's eyes, she reaches an instant, instinctual decision.
This was primal and instinctual and it gripped me like an invisible claw.
To keep a commonplace is instinctual to intellectual cultivation.
1841, from instinct (Latin instinctus) + -al (1). Related: Instinctually.
1610s (implied in instinctively), from Latin instinct-, past participle stem of instinguere (see instinct) + -ive. Related: Instinctiveness.