Intellect. An eluding concept to most. An interesting challenge to many. The word: Intellect is a noun and is observed to be the “ability to perceive, ability to reason, ability to understand, brain, brilliance, cerebration, cognitive faculty, comprehension, genius, intellectual powers, intellectuality, intellegentia, intelligence, mens, mental ability, mental acuteness, mental capacity, mental faculty, mentality, mind, power to reason, rational faculty, rationality, reach of mind, reason, reasoning faculty, reasoning power, sense, understanding.”
Intelligence is a noun and observed to be the “capacity for learning, reasoning, understanding, and similar forms of mental activity; aptitude in grasping truths, relationships, facts, meanings, etc. manifestation of a high mental capacity: He writes with intelligence and wit. The faculty of understanding.” 
That’s nice. Now what is it? Actually!
It is not a description of what it does. You wouldn’t know that by reading available definitions though. When science cannot explain something, it nearly always makes what it cannot explain into something greater than it is, in order to have something agreeable to talk about. Fact is: not one soul in science has a clue what Intelligence is, where it comes from, how it emerges, what it does in the brain and how it is totally different than what can be observed from what it results in.
Simply put: Intelligence is the degree to which process exceeds input. It means the creature with the brain can not only react to input, that creature can anticipate input, can formulate a difference to input based on previous experience with it.
Now, if Intelligence was what it is defined to be: comparing it to a simple device can explain it:
Take a radio. Any radio. Let us define a radio the same way that science dispenses with having to define intelligence.
The definition of Radio is a noun, wireless telegraphy or telephony: speeches broadcast by radio. An apparatus for receiving or transmitting radio broadcasts. A message transmitted by radio. 
But if science did not know about those pesky waves they would define a radio by observing it.
Radio is a noun and is observed to be the ability to receive, ability to amplify, ability to order stations, volume, quality, timbre, power adjustment, adjustable, carryable, sound powers, radiology, radios, radio ability, radio acuteness, radio capacity, radio faculty, radiality, songs, talk, power to receive, reach of broadcast.
Darn right stupid isn’t?!?!
The definition of Intelligence used today has no bearing whatsoever on Intelligence and in fact doesn’t require much to use it.
Intelligence is the degree to which process exceeds input.
Input is your senses. Data is received by those inputs and the brain is given that data. What does it do with it? That is the topic of a far larger paper (and books for that matter, already written and available through this site.) How does it do anything with the input? How it is that the very same neuron can process all of the senses? How can one machine process everything is the way but input is completely different and output is different as well? It takes know ‘how’ it works.
What it does, though is exactly the degree to which process exceeds input.
That means that for every chunk of input the brain will process; that chunk will be processed far more times than it will accept new input.
Easier to understand.
If you had ONE rubber ball and dropped it from 1 meter in height, the ball represents the input chunk of data. Each bounce represents a process on that chunk of data. As the ball bounces it slows down. The amount of times the ball will bounce from 1 meter in height can be said to be the ratio of process over input based on the amplitude of the ball’s bouncing.
If the ball bounced 12 times before it fell flat and stopped, the ratio could be said to be 12:1. If a ball was dropped twice a second at the same height, the ratio would still be 12:1, there would just be a separation of some duration between the balls falling. If those two criteria are variable; the ball will be processed 12 times for every drop. Step them apart by half a second and then a system is functioning where by adjusting the height of the drop the ratio can be increased or decreased. THAT is process greater than input. Your DNA will set that duration. Thank your parents.
Just like a whole is greater than the sum of its parts as it becomes a new thing made up of those parts not just a collection of parts, the brain’s process results in a whole far greater than the sum of its parts. Exponentially greater actually. Read The Brain is a Wonderful Thing for the specific Alpha Beta Theta Gamma wave calculations and where they come from.
So now.. as simple as that. You know what Intelligence is. Try it sometime. Evaluate something more than you accept it as input. Make your output based on that evaluation and not the past experience of it. Control the output by knowing how it works. See the latest video of The Price is Right 1972 to 2018 Self Awareness for how to use it.
And whatever you do; do NOT make Intelligence fit your needs. There is NO SUCH THING as Emotional Intelligence (in fact its mostly the lack of the USE of intelligence and self awareness that give rise to emotional responses.) There is NO SUCH THING as Multiple Intelligences. There is NO SUCH THING as Artificial Intelligence. There is only smoke and mirrors to keep you convinced science and industry has a handle on what they think they are doing. They don’t.