This is off-putting to atheists because they think of faith as believing without any evidence. Or believing contrary to evidence.
In other words, faith is blind.
Here is a two-stage definition of faith that I've found helpful in my discussions with atheists:
Step 1: Generic trust based on evidence.

Example: In the years leading up to 2007, both Christians and atheists drove their vehicles over the I35W bridge in Minneapolis. We trusted the engineers, the inspectors -- the whole "system" -- that built and maintained the bridge.
And we observed thousands of other vehicles successfully traversing the bridge.
Our conclusion: Venture out! Trust the steel trusses and concrete with your very life.
Christians and atheists had a ton of evidence the bridge was safe. But not proof.
In 2007 the bridge collapsed, killing 13 people.
In summary, step 1 faith is choosing to believe something based on evidence that stops short of proof.
Step 2: Personal trust and commitment. This is my faith in Jesus.
Now here's the point. As a Christian I have evidence (but not proof) that a biblical worldview is true. That's step 1, and it's pretty much the same as trusting the bridge.
Step 1 faith is what I have in common with atheists. I choose a generic kind of faith based on evidence.
But when it comes to religion, what really counts as evidence? Atheists and Christians disagree here.
I'll discuss it next week.