To speak of lavatories is U, of bathrooms non-U; to lay cloth napkins at table is U, to lay paper napkins non-U; and so on through a myriad of equally trivial examples.
not u; not characteristic of the upper classes, particularly regarding language
Silbentrennung
not u; not char·ac·ter·is·tic of the up·per classes, par·ti·cu·lar·ly re·gard·ing lan·guage