This word sure looks like cod Latin for meat, doesn’t it? Like “Omnes stuffunt meatus in mouthorum.” But there are two problems with that (aside from the extremely dodgy Latin): one, it’s not pronounced “meat-us,” it’s pronounced “me-ate-us” (/miˈeɪtəs/); two, it’s not something you stuff into a hole, it is a hole.
The Latin word meatus (with a long a) originally meant ‘path’ or ‘passage’, and came from a verb meare meaning ‘pass’ or ‘traverse’. That in turn came from a Proto-Indo-European root reconstructed as *mey- that gave rise not only to words for paths (as well as Latin trans-) but also to English mean (‘think, intend’) and, up a different path, English mean (‘common, nasty’). It even led to immune.
So what kind of a hole is a meatus? Well, it’s not a nasty, dirty, wet hole, filled with the ends of worms and an oozy smell, nor yet a dry, bare, sandy hole with nothing in it to sit down on or to eat, but it’s also not a hobbit-hole. It’s a hole in your body – the kind that is standard with the body, not the kind added by an external article of metal, stone, or wood.
There is, for instance, the meatus auditorius, also known as the auditory meatus, or the hole of hearing (that’s what one H. Crooke called it in 1615), or the earhole. Various other simple holes into the body also get called meatuses (I’m sure you can think of the most popular ones). However, it seems the mouth is not typically called a meatus – it’s too complex an opening, I think. Pity; I think I could like meatus crusti (‘cake hole’; actually Latin for ‘cake hole’ would more likely be meatus placentae, but we couldn’t use that) or perhaps meatus carnis (‘meat hole’) – though it would probably really just be something like meatus escarius, ‘eating hole’.
So there that is. You can put the figurative meat of a message or meaning into your auditory meatus, but you shouldn’t try to put actual literal meat into any meatus, especially the hole of hearing; that would be mean.