Bimonthly is a problem word, and you should treat it that way from the start. Real people use it in two opposite ways, and both show up in print. One meaning: happening every two months. A bimonthly magazine then comes out six times a year — January, March, May, and so on. The other meaning: happening twice each month, for example on the 1st and the 15th. You cannot know which one is meant from the word alone. You have to look at the rest of the sentence, a calendar, or just ask 'How many times a year?' Writers who want to be clear often avoid bimonthly and say 'every two months' or 'twice a month'. Magazines sometimes print 'bimonthly (six issues a year)' to lock it down. It can be an adjective (a bimonthly report) or an adverb (the magazine appears bimonthly). As a noun, less often, a bimonthly is a magazine of that kind. Though actually, the mess is old and has not been solved. English took bi- from Latin for 'two', but 'two' can mean 'every two' or 'two per'. The same fight sits on biweekly. If a form, a contract, or your homework uses bimonthly, do not guess.