Definition of Smart.

What is the definition of Smart?  What was the decision based on?  Are there really such a thing as "Stupid" or "Smart"?

If a person has several Ph.D's, but do not know how to do his/her own laundry, would you call him/her smart or stupid??  

If a person is a straight A student, but don't know to use mittens when taking something out of the oven, would you call him/her smart or stupid??

Or maybe there are more specific categories.  Such as a person who has done well at school, you will say  that he/she is book-smart.  I am not sure what the other term is, however.  When a person who possess lots of common sense and life experience, do you call him/her life-smart?? 

Does getting good grades really mean that the person is smart??  If a businessman with a successful business, but was a C average student and spent 6 years in college, is he smart or stupid???

I guess that there really isn't a definite answer to answer these questions.  Just something to think about.