I'm not sure about it being the opposite of everyday uses of the word, but I think you are more or less correct. But there are further complications. For example, sometimes being a reductionist about something is presented as if it were an alternative to being a realist about that something, but there is no consistency in the application of that criterion. Utilitarians are generally classified as realists about ethics, while subjectivists are generally classified as non-realists about ethics, even though both make ethical claims reducible to psychological claims. My own preference is to taboo "realism" and insist that people be more specific about what they are claiming or denying, but this this position has, alas, not yet been widely adopted by the philosophical mainstream.
Utilitarians are generally classified as realists about ethics, while subjectivists are generally classified as non-realists about ethics, even though both make ethical claims reducible to psychological claims.
That's because utilitarians make normative claims and subjectivists (of the kind you're probably thinking of) don't.
"Realism" in the philosophical sense has to be relative to something - Plato's essences, "collective imagination", society, truth are among the subjects that evoke comments that this person is a realist (considers the "something" to be real), and that one isn't.
A philosophical realist w.r.t. fairies is one who believes Fairies are real, while the non-realist says talk of fairies is due to overactive agency detectors or some such thing. It will tend to seem like the opposite of everyday use of the word "realism" -- at least if the subject is one non-philosophers would ever talk about.
I mention this only because I found it a bit difficult to get, and I think I've now "got" it. Correct me if you think I'm wrong.