To me, critical thinking means following evidence rather than beliefs, especially when evidence contradicts beliefs.
Perhaps it could be said that critical thinking is the opposite of faith?
Critical thinking also implies examining the evidence rather than just accepting it blindly.
I pretty much echo Coyote's sentiment on the definition of critical thinking.
As a sidebar, 'faith' is often used somewhat ambiguously. One can say they have 'faith' that their car will start in the morning. But it isn't a spiritual statement. At least, for most of us. One would probably be better off saying they have 'confidence' that their car will start in the morning.
Ultimately, from my view, faith at its core level means accepting something with limited to no evidence. Or perhaps, accepting something despite contrary evidence. Critical thinking means using deductive logic and evidence to draw a conclusion.