Since I re-started caving about 3 years ago, this time in Australia not the UK, I have found it interesting how familiar terms can have different meanings, depending on location and local usage. "Sump" was the first term that jumped out at me: in the UK it definitely and [i:28e6rtv4][b:28e6rtv4]only[/b:28e6rtv4][/i:28e6rtv4] means a roof-below-water passage (often alternatively called a "siphon", but that’s potentially ambiguous; and sometimes called a "water-trap"). I quickly realised that, in Australia, "sump" may be applied to any low passage that contains water and where you will unavoidably get wet. The associated feature, a passage with very low water clearance (airspace) is called a "duck" in the UK and a "roof-sniff" in Australia.
There are other examples. However, the one that has most troubled me for a long time is "Oolite". In Australia, this word (universally mis-pronounced as "oo-lite" instead of "oh-oh-lite") is commonly [b:28e6rtv4][i:28e6rtv4]mis-used [/i:28e6rtv4][/b:28e6rtv4]as a synonym for "cave pearl". We even have a cave named "Oolite Cave" at Buchan, reportedly owing to the previous presence of Oolites (ie. cave pearls). This is a usage I never encountered in England, and is not applied anywhere else (eg USA) as far as I know.
"Oolite" of course correctly means an oolitic rock, usually a limestone, formed by cementation of small spherical accretion objects known as ooids or ooliths (pronounced "oh-oids", "oh-oh-liths"). The original formation of the constituent ooids is by accretion-while-in-motion around a nucleus, similar to cave pearl formation; but they form [b:28e6rtv4][i:28e6rtv4]before [/i:28e6rtv4][/b:28e6rtv4]the limestone and are small. Larger such accretion bodies are called pisoids or pisoliths; and, if we wished to stretch a definition, perhaps "pisoid" could be applied to a cave pearl. Really though, we should use the old-fashioned but unambiguous term "cave pearl".
I half expect this post to be controversial, since in Australia the mis-usage is very widespread and will not be readily accepted as a mis-usage. It is even present in our home-grown authoritative cave-science book "Beneath The Surface".