In the earlier thread on my disdain for the z-word in reference to mixed-member systems, one comment (by Chris) suggested that a better term might be “Shadow MP”. The logic for this term is that this is what the district loser who wins via the list often does: “shadows” the winner as a second representative of the district. This makes sense, although the use of a term “shadow government” for the opposition in Westminster-type systems might render “shadow MP” confusing (as Alan suggested). ((That is, because not all “shadow” MPs are from an opposition party; they can be from the governing party in districts won by the opposition.))
Here is a good example of actual shadowing in practice!
Jacinda Ardern (“List MP based in Auckland Central”) has her office just three houses down from that of the electorate MP, Nikki Kaye.
Kaye’s office is at the left of the photo–see the blue sign behind the parked car at the left; Ardern’s is at the red sign just beyond and to the left of the motorcyclist’s head.
Here are close-ups of the offices and signs of the two MPs.
It is interesting that in New Zealand, many legislators elected via the party list, such as Ardern, refer to themselves as “List MP for” (or “based in”) whatever the district name is. However, others simply refer to themselves on the signs at their offices as a party MP. ((The example shown at that link, Tim Groser, did contest the district as well, both in 2008 and 2011.)) Surprisingly, I did not see one sign that said “Zombie MP for…”