I don't think it's possible to have a universal "colloquial" definition of "simple" that is also precise. It's all relative.

This is why I think the formalists studying complexity back in the 50s had the right approach. You can only give "simple" precise meaning within some kind of formal system with a shared set of initial axioms or assumptions. From that point you can define it quantitatively over some set of objects (relations, programs).

Funnily enough, this approach also touches on Hickey's etymological derivation. The root words also fundamentally have to do with the quantity of relationships.