Sir A's right, it's correct if you think of how different it is from vertical, rather than from horizontal. But I think the problem is that someone has taken a relatively logical phrase, "steeply raked," and shortened it to "steep" so it means nothing at all. "Slanted" would work.
But a lot of these idiocies make it into common usage despite being illogical. Try this one: "transparent" decision-making processes that they are always promising in governments and so on. "Transparent" means something is essentially invisible. The word they want is "visible."
My dad's pet peeve is "warm temperatures." Temperatures are either high or low, but they aren't warm or cold.
Anyway, the glass in front of me towers up almost two metres and thanks to good wiper blades, opposable wiping, rain-x, and a microfibre wipe inside - vision couldn't be clearer.
Umm... "What is a bus?"