Excuse me tearing my hair out, but I’ve just seen this recommended yet again, and it’s in several dictionaries, and it is wrong!
Under German law, a testator may leave stuff to a Vorerbe (prior heir) and a Nacherbe (subsequent heir). In the usual case, maybe a house to A for life, and when A dies, then to B.
That’s a bit like a life interest and a remainderman (remainderperson in some U.S. usage). A trust arises in English law, but the situation is similar. The remainderman gets what’s left.
These trusts can be quite complex. The testator may leave the estate to A for life, with remainder to B for life, and in that case, since clearly B’s heirs are not included, on B’s death the estate will revert to the testator – or rather, since the testator will be dead, it will revert to the testator’s heirs on intestacy (gesetzliche Erben). They are the reversioners.
It’s not a secret that revert means come back, is it?
But a Nacherbe is not a reversioner, not the heir(s) on intestacy of the testator. It might happen by coincidence, but that is not the definition. If any of those words fit, it will be remainderman, but since that’s a rather old-fashioned word unknown to the general public, people may want to write subsequent heir or final heir or something like that.
I haven’t got one law dictionary here that does not contain reversionary heir, sometimes alone (Dietl), sometimes as one alternative (Romain, von Beseler/Jacobs-Wüstefeld, Lister/Veth).