Anecdata: to me and others I've spoken to 'passion' is short hand for a person having personal work standards. i.e.: a person who won't half-ass their work, who'll often go the extra distance for polish or feature completion, and who'll proactively help raise issues if their experience indicates the team is heading down the wrong path.

And yes, a person who'll very occasionally stay late and pitch in when the whole team is crunching on something.