Also found in: Dictionary, Thesaurus, Medical, Financial, Encyclopedia, Wikipedia.

base instinct

A subconscious urge, behavior, or intuition directed by primeval, animalistic, self-serving, or ignoble motivations. Greed and selfishness are unfortunately two of the base instincts ingrained in the human psyche. Though he is an upstanding citizen, when he drinks, he unfortunately succumbs to his base instincts.
See also: base, instinct

gut instinct

An intuition or feeling, as opposed to an opinion based on a logical analysis. My gut instinct about Kara's new boyfriend proved correct when we discovered he had a pretty extensive criminal history.
See also: gut, instinct

killer instinct

An innate or intuitive inclination and ability to do whatever is necessary in order to succeed, no matter how ruthless. She has the killer instinct needed to claw her way to the top of the industry. You've got book smarts, kid, but you'll never make it as a lawyer if you don't have a killer instinct.
See also: instinct, killer

killer instinct

Cliché an inborn desire or ability to be ruthless. Fred has a real killer instinct. He's a difficult boss to work for.
See also: instinct, killer
References in classic literature ?
Slave-making instinct. -- This remarkable instinct was first discovered in the Formica (Polyerges) rufescens by Pierre Huber, a better observer even than his celebrated father.
Smith, I tried to approach the subject in a sceptical frame of mind, as any one may well be excused for doubting the truth of so extraordinary and odious an instinct as that of making slaves.
Such are the facts, though they did not need confirmation by me, in regard to the wonderful instinct of making slaves.
It will be universally admitted that instincts are as important as corporeal structure for the welfare of each species, under its present conditions of life.
As some degree of variation in instincts under a state of nature, and the inheritance of such variations, are indispensable for the action of natural selection, as many instances as possible ought to have been here given; but want of space prevents me.
Several cases also, could be given, of occasional and strange habits in certain species, which might, if advantageous to the species, give rise, through natural selection, to quite new instincts. But I am well aware that these general statements, without facts given in detail, can produce but a feeble effect on the reader's mind.
How strongly these domestic instincts, habits, and dispositions are inherited, and how curiously they become mingled, is well shown when different breeds of dogs are crossed.
Domestic instincts are sometimes spoken of as actions which have become inherited solely from long-continued and compulsory habit, but this, I think, is not true.
Natural instincts are lost under domestication: a remarkable instance of this is seen in those breeds of fowls which very rarely or never become broody,' that is, never wish to sit on their eggs.
(4) That instinct supplies the impulses to experimental movements which are required for the process of learning;
All the above characteristics of instinct can be established by purely external observation, except the fact that instinct does not require prevision.
Moreover, "the well-being of the individual and the preservation of the race" is only a usual characteristic, not a universal one, of the sort of movements that, from our point of view, are to be called instinctive; instances of harmful instincts will be given shortly.
We may say that an "instinctive" movement is a vital movement performed by an animal the first time that it finds itself in a novel situation; or, more correctly, one which it would perform if the situation were novel.* The instincts of an animal are different at different periods of its growth, and this fact may cause changes of behaviour which are not due to learning.
To begin with, many instincts mature gradually, and while they are immature an animal may act in a fumbling manner which is very difficult to distinguish from learning.
(5) That instincts in their nascent stages are easily modifiable, and capable of being attached to various sorts of objects.