[smif]

What lay people mostly mean by 'relative' is subjective; ie., they're committing the genetic fallacy of the form: since understanding X requires a perspective in which to evaluate it, X itself must be a (inter)subjective phenomenon.

ie., they're saying that since understanding is relative to a perspective so is what is understood. This is the irritating fallacy popular amongst those who go around abusing the term 'relative'.

I'm not sure if I find this particularly convincing. I think most lay people are actually talking about the thing itself rather than their understanding/perspective on the thing.

Maybe this is something that a study could shed light on, if we're able to construct a survey that can give us some insight into how lay people are using/abusing these terms.