I've always,with my lack of formal training..considered intelligence as the capability to absorb knowledge quickly and also utilise whatever native abilities you posess to rapidly diagnose and repair whatever is broken and/or malfunctioning,chiefly from a mechanical standpoint,but also from a human angle as well,the more you know people,the sharper your instincts and the less you expect of them,ergo,the easier to manipulate them and sooth their wounded egos.
On the flip side,the easier to make a profit from your fellow beings.