The fashionable commonplace used to shout down religious believers is this:
“Faith is belief without evidence.”
If you pry at this simplistic and decidedly question-begging "definition" you will find, though, that what the accuser really means is:
“Faith is belief without scientific proof.”
Scientific proof being the only kind of evidence that the non-believer will typically accept from the believer.
But of course, no Christian ever claimed that Christianity was absolutely proven, and no Christian ever asserted that Christianity was primarily held as true on the basis of science, even though some scientific findings may support certain propositions in the Christian faith.
What this definition reveals is not that Christian faith is narrow-minded, but that the non-believer who asserts this definition has a narrow understanding of both faith and human knowledge generally.
In fact, most Christians hold something like this:
“Faith is trust in God, whom we have good reason to believe exists, and believing what we have good reason to think God has revealed.”
Where "good reason" can be taken to mean "evidence" so long as you do not insist on reducing "evidence" to "scientific proof."
Many Christians have thought down through the ages that the proposition "God exists" is something that can be demonstrated:
“But against this argument the apostle [Paul] says (Rom. I., 20), “The unseen things of God are visible through His manifest works.” But this would not be so unless it were possible to demonstrate God’s existence through His works. What ought to be understood concerning anything, is first of all, whether it exists. Conclusion. It is possible to demonstrate God’s existence, atthough not a priori (by pure reason), yet a posteriori from some work of His more surely known to us.”
The Christian believes that God exists because God's existence is demonstrable, though not scientifically provable, and that this demonstrability rests not on the Bible but on nature and reality itself (thus the various "proofs" of God's existence). Faith in God's existence is necessary, however, because the slings and arrows of outrageous fortune make it possible at times to forget the evidence, and so we require the tenacity to hold on to what we otherwise know to be sound belief.
Faith is further required to believe in the particular propositions put forward by Christianity, for while God's existence may be demonstrable, Christ's identity can only be verified on the basis of purported divine revelations. But the Christian has reasons for trusting those revelations, so even here his faith is founded on evidence, even if that evidence is not scientific, and even though it does not constitute proof.
Of course, the non-believer can legitimately disagree about whether the demonstrations of God's existence succeed and whether the evidence for the truth of Christian revelation is strong evidence. That's fine. A discussion about the nature, extent, and particulars of the evidence claimed by Christianity is necessary and fruitful.
What is not fruitful is to assert (a) that Christian faith is by definition devoid of and inimical to evidence, and (b) that there isn't any evidence anyway. That move is full-on fingers-in-ears infantile, a merely rhetorical tactic unbecoming of supposed critical free thinkers, and it evinces a deep disrespect and misunderstanding of one's Christian opponents.
Intelligent people are better than that, so let's leave aside such a silly definition.