Definitions: (1) having an active, discerning, or acute mind; knowing; understanding; (2) sensible wisdom; (3) guided or directed by a keen mind; rational; (4) well-informed and accurate information <a good decision precluded by good intelligence>
Synonyms: Intelligent stresses success in coping with new situations and solving problems; alert stresses quickness in perceiving and understanding; clever implies a native ability or aptness; quick-witted implies promptness in finding answers in debate or humor, or in devising expedients in moments of danger or challenge.
Ignorance leads to fear, fear leads to hate, hate leads to violence. This is the equation. An army of philosophers would not be sufficient to change the nature of error and to make it truth. — Ibn Rushd [Averroes] (1126-1198) Muslim Scholar
Comment: If you believe you are not intelligent, you are probably underestimating yourself. Test your limits. You will tend to hold yourself within what you think to be true. You can always underestimate and be more confident of success, but if you overestimate, with a dash of prudence (and a modicum or courage and luck) you will attain greater results.
There are nine types of intelligence: linguistic, logical/mathematical, musical, visual/spatial, kinesthetic, naturalist, knowing oneself, knowing others, existential. — Howard Gardner (1943 -) Frames of Mind
Note: You have all types of intelligence – all of which are integrated to some degree. What is important is to keep expanding all areas of yourself (not just intelligence). It is easier to do so in the area(s) that is (are) comfortable, but it is possible to develop the other areas as well. Do this by putting yourself into the path of learning, and by dealing with conflict as you move through life.