For me slips up happen in the moment more on impulse than anything else.
I class it as more as relapse when I start to plan behaviours and how to hide it in advance rather than it being more reactive.
That said when I get a succession of slip ups in an extended period I would also class it as a relapse.
Do you want to talk about it? Recovery isn't linear, I know you don't need me to tell you that but it is sometimes a good thing to remind ourselves! Relapse or slip up, to some degree is semantics how you respond to them is what matters. Face it head on before you fall in too deep.