So what are Slash Stars?

I’m currently researching more exotic spectral types of stars for a presentation and while researching I came across so called “slash stars”. The name seems to derive from the slash within their spectral classification (i.e. something like O2.5If\*/WN6) but I don’t really understand what they are because apparently they are technically class O stars but also somehow Wolf-Rayets? This seems to be quite niche so I was hoping someone might be able to explain it a bit more simple than the sources I’ve found up to this point.

Oh and also as a bonus if you know of any spectral-class-peculiarities that aren’t well know do please mention them…I’d like to have a wide array of examples beyond the classic OBAFGKM and currently I’m only working with what Wikipedia has mentioned in their stellar classification page as well as some just weird examples of star evolution (like kerr-black holes for example) but I would love to have some other oddities