Critical thinking, as the term is generally used these days, roughly means reasonable and reflective thinking focused on deciding what to believe or do.  

Ideal Critical Thinkers

1.  Care that their beliefs be true,  and that their decisions be justified; that is, care to "get it right" to the extent possible. A critical thinker
     a. seeks alternative hypotheses, explanations, conclusions, plans, sources, etc., and be open to them.
     b. endorses a position to the extent thatit is justified by the information that is available.
     c. is well informed.
     
2.  Care to present a position honestly and clearly, theirs as well as others'. A critical thinker
     a.  is clear about the intended meaning of what is said, written, or otherwise communicated, seeking as much precision as the situation requires.
     b.  determines, and maintains focus on, the conclusion or question at hand.
     c.  seeks and offer reasons.
     d.  takes into account the total situation.
     e.  is reflectively aware of their own basic beliefs.

3.  Care about the dignity and worth of every person. A critical thinker
     a.  discovers and listens to others' view and reasons.
     b.  avoids intimidating or confusing others with their critical thinking prowess, taking into account others' feelings and level of understanding.
     c.  is concerned about others' welfare.