The first definition of divine is what belongs to God, or to the gods.
This value is mostly religious, but it has other significations that aren’t religious.
For non believers, divine is an adjective that refers to something excellent, perfect : we especially use it to talk about a dish or someone’s beauty (see beauty).
For a believer, everything that is divine must be respected and praised according to every religions’ rituals. While, for an atheist, something is divine when this thing is getting so close to perfection that we have to respect it and its creator when there’s one.