No Useless Words!

A thread on "useless words" has been started over at the Fortean Times message board (I'd link you, but the site requires registration to read posts, I believe); but I don't think most of the instances cited are useless at all! The OP leads with "freshet," for example, and though it's not in every day use I can't possibly be the only person left in the world who understands it. It's used in poetry, and provides an attractive alternative to "water run-off" and "flooding," especially in cases of violent activity.

Some words nominated which I wouldn't have even considered obscure are "incunabulum," "timorous," "prolix," and "dilatory." As far as I know, incunabulum is the only available word for an early printed book, and anyone who reads Dorothy L. Sayers knows what it means, because Sir Peter Wimsey collects them. I don't routinely use timorous or prolix, but I read them occasionally, and would expect to be understood if I used them in conversation. "Dilatory" I do use routinely. I have a friend who's dilatory (as well as prolix!), and I tell him so; plus I occasionally apologize for being that way myself online.

Others are useful and should be more widely known, especially:

Mumpsimus (n.): 1. A view stubbornly held even when shown to be wrong.
2. One holding such a view.

Omphaloskepsis (n.) Navel-gazing. This refers to introspective self-analysis.
Etymology: Greek, from omphalos, “navel” and skepsis, “query or doubt.”

and
Growlery (n.): A retreat for times of ill humour.

Others are obscure only because they are jargon, and are not only useful but essential within certain fields of endeavor, such as
Almacantar (n.): A circle of altitude, parallel to the horizon. An astronomical term, used to describe imaginary lines in the sky by which an astronomer determines the height of a star in the sky relative to the horizon.

Haecceity (n.): The aspect of existence on which individuality depends; the hereness and nowness of reality.

Skeuomorph (n.): A retained but no longer functional stylistic feature.

Ullage (n.): The amount by which a cask or bottle falls short of being full
Etymology: From Anglo-French ulliage.

Boustrophedon (adj. and adv.): Of writing, alternating left to right then right to left.
Etymology: Greek, from bous, “ox” and strophe, “a turning.”

Keeping track of ullage is vital in the safe storage of volatile liquids such as petroleum, so this word stands in well as an argument for the usefulness of jargon. Outsiders won't often need to follow the conversations that require jargon anyway, and can learn the meaning of the uknown term in about two seconds, if they do.

Other words, of course, are beautiful in their own right, as sounds and as concepts, such as:
Mascaron (n.): A grotesque face on a door-knocker.

Antiscian (adj., n.): Those who live on the same meridian, but on opposite sides of the equator so that their shadows at noon fall in opposite directions

and the wonderful
Incompossible (adj.): Not mutually possible. Not possible together; wholly incompatible or inconsistent.

I often encounter reverse vocabulary-snobbery, when people get angry at me for using a word that they don't know but which is part of my normal usage. Learning new words is easy. Your brain is adapted to it, and does so all the time. Every language (but particularly an etymological packrat language like English, which not only is constructed to enable new coinages but routinely borrows from every other language it encounters) contains more words than any one person can learn in a lifetime; so the mysterious Language Acquisition Device of the brain never loses its capacity for lack of use.

If someone uses a word you don't understand, look it up, or ask for clarification. It's a reasonable request.

Far more reasonable than expecting people to instinctively know which words in their vocabulary aren't in yours, and limit their communication accordingly!

Learn new words,
But keep the old!
One is silver
And the other, gold!