Biweekly
You can add “biweekly” to the list of words that are now unusable: in some parts of the world it has come to mean twice a week, whereas apparently it originally meant every two weeks. All a bit rubbish really. A quick googling found I'm not the only person who thinks that we should have diweekly (language NSFW) for the former and biweekly for the latter, but I don't see it happening.