subjective means subjective and false means false. they are just harmonies. a subjective statement is a false objective statement. a false statement is only viable as a subjective statement, and worthless as an objective one. One can infer objective falseness from a subjective statement.
since subjectivity is likend to one's inner world or experience, it is therefore the distinguishable opposite of objective, which refers to mutually observable' information in our shared environment,which can only provide what we can call 'truth'.
Our one shared environment is objective reality. Our unique environment is our internal world. Note there is one distinction for objective reality, one 'count', and very large number of 'subjective' realities experiencing it.
"Subjective" doesn't mean "objectively false" either. There is a very distinct difference. "Subjective" implies only that the statement pertains to the thinker, not the object of thought.
Anyway, you asked for something that wasn't in the dictionary, and neither "false" nor "objectively false" is a definition for the word "subjective".
ETA: Unless, of course, you're using some freaky-ass dictionary.