“A mighty fortress is our God, a bulwark never failing.” Dude, what’s a bulwark?

Zach: “A mighty fortress is our God, a bulwark never failing.” Dude, what’s a bulwark?
Brian: What?
Zach: It says, a bulwark never failing.
Brian: I think it’s a wall.
Zach: Then why don’t they just say that? Bulwark sounds totally gay.
Brian: I don’t think you’re supposed to call a hymn gay. It’s like a sin or something.
Zach: Whatever, man. I’m not saying bulwark.