In Pali Buddhism, what is not mundane is defined by the word 'lokuttara', which means 'beyond the world', 'supramundane' or 'transcendent" &, most importantly, equates with the realisation of 'emptiness' ('sunnata'), 'not-self' ('anatta') or selflessness. To quote:
Ye te suttantā tathāgatabhāsitā gambhīrā gambhīratthā lokuttarā suññatapaṭisaṃyuttā
We will listen when discourses that are words of the Tathagata — deep, deep in their meaning, transcendent, connected with emptiness...
Therefore, unless the mind is, at least, Sotapanna, everything experienced is 'mundane'.
Contrary to the above, what is 'mundane' in Pali Buddhism is described as follows:
What is right view affected by the taints, partaking of merit, ripening in the acquisitions?
There is what is given and what is offered and what is sacrificed; there is fruit and result of good and bad actions (kamma); there is this world and the other world (paraloka); there is mother and father; there are beings who are reborn spontaneously (sattā opapātikā); there are in the world good and virtuous recluses and brahmins (samaṇabrāhmaṇāsamaṇa) who have realised for themselves by direct knowledge and declare this world & the other world.
Therefore, included with the ordinary world of common conventions, the following Buddhist topics are also 'mundane':