What do people mean when they say they disapprove of abortion as "birth control"?

Steph at Grounded Parents has a great piece addressing some of the problems with people who say, "I'm pro-choice but I don't think women should be allowed to use abortion as birth control." You see this sentiment a lot and it's not so much a coherent policy position as an attempt by the speaker to impress you with how they're a more morally serious person than all those sluts they assume are clogging up the Planned Parenthood. Of course, saying this disproves that one is a morally serious person, because it shows that you don't research your opinions before you form them and that you're more interested in showing off than you are giving a moment's thought to the consequences of your beliefs. Steph debunks this mentality by laying out the substantial evidence that women do not take the abortion decision lightly, do not have "frivolous" reasons for abortion, and generally make some effort at preventing unwanted pregnancy in the first place. It's a good post. You should read it.

I just want to pivot from here and say that the "abortion as birth control" complaint makes me crazy because it makes no sense. I can never figure out what people are trying to say by "using abortion as birth control".  If we take the statement literally, then it's moronic, because all abortion is fundamentally about birth control, in the sense that you are trying to prevent a woman from giving birth. That's true even for abortions done to save the mother's life: Because childbirth will kill her, we control the birth so it does not happen. This is tautological, really.

But clearly, people who say this aren't speaking literally. By "birth control", they are trying to invoke this idea that women are being too sexual or too frivolous or are too interested in not giving birth right now. But they very rarely, if ever, define what makes an abortion "birth control" and when it's not "birth control". Considering that this is not, though many people mistakenly believe otherwise, an abstract debate about what you believe in (as if anyone gives a hoot), but is actually a debate over what legal rights women have, this lack of definition is maddening. How can you ban these "birth control" abortions if we don't even know what counts as a "birth control" abortion? How will we determine which abortions are allowed and which are not if you won't even define your terms? The fact that people who say this haven't ever considered these questions shows that they are very much not morally serious people and should really learn to shut their fool mouths until they learn to think before speaking.

But perhaps I'm being a bit unfair. Perhaps there is some commonly understood meaning of what someone means when they say they oppose using abortion as birth control, and I'm just too literal-minded to see what it is. So I thought I'd turn the question over to you, Pandagon readers. You're smart people who are out there discussing this issue with others so I'm sure you hear this sentiment a lot. What do you think people commonly mean by it? I came up with some options to vote on, but if you have other ideas, feel free to share in comments!