As usual, it takes a philosopher to sort out the various meanings and arrive at a reasonable definition. (Philosophers are experts at critical thinking, although they often use it when it's not necessary.) Read what John Wilkins has to say at: What is critical thinking. Contrast his critical thinking about the subject with that illustrated in the Wikipedia article on Critical Thinking.
Here's his bottom line but you really need to see his examples of what is not critical thinking.
Critical thinking is the application of careful analysis and rational reconstruction to arguments, so that the correctness of the reasoning and the truth of the premises can be evaluated and the support for the conclusion determined.I agree with John and this is what Chris DiCarlo and I teach in our course. But, you should read the comments on John's blog.
Rational thinking is the assent of the reasoner to any conclusion that is both correctly reasoned and founded on known to be true, or likely to be true, premises.
In short, a critical and rational thinker is one who accepts the conclusions of good arguments.
Once you've mastered the basic rules of logic, most arguments should be about whether the premises are likely to be true.