This is because, while my all-fees-paid scholarship placement there certainly benefitted me in the long run, it's only on balance over my five years of attendance there that I could say I enjoyed it more than I hated it. I made some good friends (all of whom I then lost touch with completely), and I owe a great deal to certain teachers, but the school as a whole... pfft.
Boarding-schools (not that I ever boarded, thank God, or I would have gone mental) are hermetic subcultures, geographically isolated, with limited channels to the outside world. Considered as speech-communities, their language can evolve in some peculiar and baroque ways.
For a while I've been thinking that it might be a service to philology (albeit a minor service, probably performed in a tiny rural church at 11 o'clock at night according to a scandalously misprinted prayer-book all copies of which were supposedly burned in 1762) if I documented some of the weirder slang that was in currency at the school between 1985 and 1990. Preferably before it all falls out of my head, as much of it has done already.
What follows, then, is a brief dictionary of (what I remember of) Lancing College slang of the late 1980s, with notes.
Some of this language was doubtless transitory, some perennial enough that I'm sure it must survive today. A lot of it's also self-evidently ridiculous, which is why it's hilarious to remember my contemporaries (and, to be scrupulously fair, me) using it in all seriousness as part of our adolescent dominance-rituals. What knobs we were.
- amphi, n. The school amphitheatre, used for open-air drama and illicit smoking.
- dodds, n. A clumsy person. (An eponym, obviously. During my time at Lancing it was gradually giving way to barclay, n., after a particularly unfortunate classmate of mine.)
- dossage, n. Relaxation, laziness. (Etymology obvious, and I'm surprised it isn't in wider use.)
- foetus, n. A stupid or useless person. (Used as a general all-purpose insult with truly astonishing ubiquity. Quite how this state of affairs first arose, I couldn't even begin to speculate.)
- glip, v. Masturbate (of a male). n. (Male) masturbation, semen. (Onomatopoeic, presumably, although to be honest I'd rather not think about it. I don't think the possibility of female masturbation really figured as a concept for any of us, except presumably the sixth-form girls.)
- glip-rag, n. Handkerchief etc used to clean up after masturbation.
- grove, n. Toilet. (This one was historic -- none of my contemporaries actually used it. The only people who did were a few nostalgically-minded masters who found the equally pastoral-sounding "bog" aesthetically troubling.)
- Head Man, n. Headmaster (or school principal, for those of you who were born after 1980 / in the United States and have never read The Beano. This is another one the masters used more than the pupils.)
- herman, n. Person with ginger hair. (As clear an illustration of metonymy as I've ever seen. The word originally applied to a boy nicknamed "Herman" because of his close physical resemblance to Herman Munster -- a resemblance which his ginger hair marred only slightly. Before long, however, it was assumed that gingerness was the defining characteristic of a "herman", and the Munster connection was forgotten entirely. I heard this applied to petite, pretty redheaded girls.)
- irrelevant, adj. Keeping a low profile, and therefore unlikely to be widely recognised. (Not knowing someone in your year was usually a major social faux pas, so I suspect the cool kids made this one up to mean it wasn't bad when they did it.)
- juvie, n., adj. (Person showing signs of being) marginally more immature than oneself at a particular moment.
- pitt, n. Study-bedroom. (This one was in official use, and had probably been so since the first such rooms were adopted at the school. It was always spelt with the double "t", suggesting that the etymology wasn't the obvious one.)
- prole (also proll), n. Member of the working classes, particularly the support staff. (This wasn't, of course, unique to Lancing, but it was shockingly universal among the pupils there. More interesting than the simple fact of its use were the limits of the same: the school librarian, for example, an educated, clearly patrician man, was never a "prole" -- although nor was the School Marshal, a distinctly working-class ex-army N.C.O. dragooned into instilling some semblance of discipline into the pupils. That may just be because we were too scared of him, though. Groundskeepers, cleaners, kitchen staff, people who served you in shops, students at state schools -- all of these were "proles".)
- rip, v. Mock, tease, ridicule. (For some reason outsiders were always surprised to discover that our use of "ripping" differed from that current at Malory Towers in the 1940s.)
- ronnie, n. Short person. (A somewhat less extreme parallel to herman (q. v.), since being short was at least one of the characteristics which the history master nicknamed "Ronnie" shared with Ronnie Corbett, rather than one of the few which distinguished them.)
- smeggy, adj. Smelly, disinclined to wash. (Derivation obvious, and deeply unpleasant.)
- square, n., adj. (One who is) hard-working and clever, and thus not cool. (I can only assume that "square" had been applied to overly conformist pupils in the late 60s, and had shifted its focus since then.)
- twos, n. See below.
- vegetable, n. One who fails to enjoy, or does very little, exercise. (This, like "square", was usually applied to me.)
- wicked, adj. Ugly. (Used of boys who were considered hideously, fantastically grotesque, and any girl who wasn't a potential supermodel.)
I may well add to this as more words come to me. If you were at Lancing during the relevant period and have (somehow) found your way here, do feel free to comment with further examples.
[Edit 6/12/2007 to add "rip" and "twos".]
 The School Marshal during my early years at Lancing was a huge, terrifying man who died tragically and heroically on holiday, saving his fellow-passengers from the capsize of the Herald of Free Enterprise. I couldn't stand him, but that's scarcely the point.