When you consider dictionaries, they often focus on mainstream published sources. Programming is a specialized field and "semaphore" in the multi-threading sens

When you consider dictionaries, they often focus on mainstream published sources. Programming is a specialized field and "semaphore" in the multi-threading sense has not entered into common usage, so it would be unlikely to be present in the corpus that they're working with. You could argue that dictionaries should cover every argot, but that requires resources and people who specialize in those fields. Programmers would be better served with a specialized dictionary,[0] especially since your average Joe isn't usually going to see it being used outside of the specialized field. [0]: And we do have those. For example: http://foldoc.org/semaphore http://foldoc.org/semaphore. HN might especially be interested in the Jargon file: http://catb.org/jargon/html/ http://catb.org/jargon/html/.