instinct (n.)

early 15c., "a prompting" (a sense now obsolete), from Old French instinct (14c.) or directly from Latin instinctus "instigation, impulse, inspiration," noun use of past participle of instinguere "to incite, impel," from in- "into, in, on, upon" (from PIE root *en "in") + stinguere "prick, goad," from PIE *steig- "to prick, stick, pierce" (see stick (v.)).

Meaning "animal faculty of intuitive perception" is from mid-15c., from notion of "natural prompting." General sense of "natural tendency" is first recorded 1560s.

Instinct is said to be blind--that is, either the end is not consciously recognized by the animal, or the connection of the means with the end is not understood. Instinct is also, in general, somewhat deficient in instant adaptability to extraordinary circumstances. [Century Dictionary]

updated on September 25, 2018

Definitions of instinct from WordNet
instinct (n.)
inborn pattern of behavior often responsive to specific stimuli;
altruistic instincts in social animals
the spawning instinct in salmon
Synonyms: inherent aptitude
instinct (adj.)
(followed by `with') deeply filled or permeated;
words instinct with love
Synonyms: replete
Etymologies are not definitions. From, not affiliated with etymonline.