impulse

im·pulse

noun \ˈim-ˌpəls\

Definition of IMPULSE

1

: a wave of excitation transmitted through tissues and especially nerve fibers and muscles that results in physiological activity or inhibition

2

a : a sudden spontaneous inclination or incitement to some usually unpremeditated action <some uncontrollable impulse…may have driven the defendant to the commission of the murderous act—B. N. Cardozo> b : a propensity or natural tendency usually other than rational <the fundamental impulse of self-expression—Havelock Ellis>