Intuition is the apparent ability to acquire knowledge without inference or the use of reason.
“The word ‘intuition’ comes from the Latin word 'intueri', which is often roughly translated as meaning ‘to look inside’ or ‘to contemplate’."
Law enforcement officers often claim to observe suspects and immediately "know" that they possess a weapon or illicit narcotic substances. On such occasions, these officers are unable to articulate their accurate reactions that may represent building blocks to reasonable suspicion or probable cause indicators. Often unable to articulate why they reacted or what prompted them at the time of the event, they sometimes retrospectively can plot their actions based upon what had been clear and present danger signals. Intuitive abilities were quantitatively tested at Yale University in the 1970's. While studying nonverbal communication, researchers noted that some subjects were able to read nonverbal facial cues before reinforcement occurred.  In employing a similar design, they noted that highly intuitive subjects made decisions quickly but could not identify their rationale. Their level of accuracy, however, did not differ from that of nonintuitive subjects..
“Intuition is a combination of historical (empirical) data, deep and heightened observation and an ability to cut through the thickness of surface reality. Intuition is like a slow motion machine that captures data instantaneously and hits you like a ton of bricks. Intuition is a knowing, a sensing that is beyond the conscious understanding — a gut feeling. Intuition is not pseudo-science.” Abella Arthur
In personality assessment
Intuition is one of Swiss psychologist Carl Jung's four 'psychological types' or ego functions. In this early model of the personal psyche, intuition was opposed by sensation on one axis, while feeling was opposed by thinking on another axis. Jung argued that, in a given individual, one of these four functions was primary — most prominent or developed — in the consciousness. The opposing function would typically be underdeveloped in that individual. The remaining pair (on the other axis) would be consciously active, but to a lesser extent than the primary function.  This schema is perhaps most familiar today as the Myers-Briggs Type Indicator.
In psychology, intuition can encompass the ability to know valid solutions to problems and decision making. For example, the recognition primed decision (RPD) model was described by Gary Klein in order to explain how people can make relatively fast decisions without having to compare options. Klein found that under time pressure, high stakes, and changing parameters, experts used their base of experience to identify similar situations and intuitively choose feasible solutions. Thus, the RPD model is a blend of intuition and analysis. The intuition is the pattern-matching process that quickly suggests feasible courses of action. The analysis is the mental simulation, a conscious and deliberate review of the courses of action.
An important intuitive method for identifying options is brainstorming. According to the renowned Neuropsychologist and Neurobiologist Roger Wolcott Sperry though, Intuition is a right-brain activity while Factual and Mathematical analysis is a left-brain activity.
The reliability of one’s intuition depends greatly on past knowledge and occurrences in a specific area. Someone who has more experiences with children will tend to have a better instinct or intuition about what they should do in certain situations. This is not to say that one with a great amount of experience is always going to have an accurate intuition (because some can be biased); however, the chances of it being more reliable are definitely amplified.