Wittol (a man who tolerates his wife’s unfaithfulness), alienism (the study and treatment of mental illness) and woolfell (the skin of a sheep with the fleece still attached) are among the words that have been identified by the dictionary publishers Collins as now obsolete. They will still appear in the large Collins dictionary, but will be dropped from future editions of smaller dictionaries.
Some of the words on the list are old-fashioned methods of transport or transport-related words, including cyclogiro (an aircraft propelled by rotating blades), charabanc (an old coach) and aerodrome (a landing area, smaller than an airport). Other words that are no longer used include: succedaneum (something used as a substitute), and supererogate (to do more than is required).
Collins has identified words that have changed in meaning over time, for instance fun fur, which in the 1960s was cheap, but real, fur, eg from rabbits, whereas nowadays it means faux, or artificial, fur.
Predictably, readers have left comments bemoaning the disappearance of their so-called favourite words (charabanc is popular) from dictionaries, but Collins is only referring to their pocket and smaller dictionaries where space is limited. Plenty of people insist that the words aren’t obsolete, and, of course, for some people they aren’t. If you live in Redhill, Surrey, you will definitely know the word aerodrome because the town has got one – it’s only ever called Redhill Aerodrome. If you like reading Agatha Christie books, or books about Billy Bunter, you’ll probably have seen ‘charabanc’.
For a few more words on Collins' endangered list see this article.