flat vs level

A couple of weeks ago Martha made reference to a plumb line being perpendicular to a flat surface which is WRONG. A plumb line is perpendicular to a level surface - an entirely different thing. I'm surprised Martha made such an error!
Well, holy crap! Somebody chase her down and stone her!
Actually, now that I look at my dictionaries, I see that the first definition of flat is “horizontal, level” in Collins and in 2a of Merriam-Webster's Collegiate as “having a continuous horizontal surface.”
It's convenient to decide that a word has just one meaning so you can leap on someone and score cheap points to make yourself feel good but it's the wrong kind of behavior.

Grant Barrett said:
Well, holy crap! Somebody chase her down and stone her!
Actually, now that I look at my dictionaries, I see that the first definition of flat is “horizontal, level” in Collins and in 2a of Merriam-Webster's Collegiate as “having a continuous horizontal surface.”
It's convenient to decide that a word has just one meaning so you can leap on someone and score cheap points to make yourself feel good but it's the wrong kind of behavior.
Well, I agree that flat can mean the same thing as "level," but I think I'd cut rsteiner a little bit of slack, since it seems that that meaning of "flat" doesn't get used nearly as often these days, and that "flat" now usually refers to the surface of an object, and does not necessarily mean that the object is horizontal relative to the earth. I know I usually hear / read "level" used for that meaning.
I don't think I'm going to cut slack on this one. If someone is going to complain, they're going to be held to a high standard of evidence. Especially given the context of the conversation, in which it was really very clear what we were talking about and what was meant. To misunderstand what Martha said you have to choose to misunderstand. That is, you have to want to pick a fight over nothing for no good reason at all.
As for the comment "it seems that that meaning of 'flat' doesn't get used nearly as often these days": prove that. I don't think you can. You made it up and added the "seems" as a hedge word to help cover yourself.
This isn't one of the places on the Internet where one can just make things up (or offer uninformed peeves) and expect them to fly.

Grant Barrett said:
I don't think I'm going to cut slack on this one. If someone is going to complain, they're going to be held to a high standard of evidence. Especially given the context of the conversation, in which it was really very clear what we were talking about and what was meant. To misunderstand what Martha said you have to choose to misunderstand. That is, you have to want to pick a fight over nothing for no good reason at all.
As for the comment “it seems that that meaning of ‘flat' doesn't get used nearly as often these days”: prove that. I don't think you can. You made it up and added the “seems” as a hedge word to help cover yourself.
This isn't one of the places on the Internet where one can just make things up (or offer uninformed peeves) and expect them to fly.
Well, no, I don't have any proof of that, it's just my own personal observation. I did NOT "make it up," and I would appreciate an apology for your insult to my integrity.