<noun> British slang Male ejaculate, semen, penile ejecta, a bomb-load of jizz.
Seeing as sperm is the cause of 99.9% of pregnancies - resulting in babies - it was only a matter of time before someone made the connection between sperm and babies and formed the phrase Baby batter as a metaphor for come/cum.
Very simply male ejaculate. One of many ingredients in the recepie that is a child, it is available whenever needed by a woman. Although it is meant to create babies it usually slams against a laytex membrane (sometimes flavored) or a kleenex.