Does bimonthly mean "twice a month" or "every two months"?

Unfortunately it means both! In the publishing industry, though, it's used fairly consistently to mean 'every two months', so that a bimonthly magazine is generally one that's issued every two months. The same ambiguity affects biweekly and biyearly. If you want to be absolutely clear, it's best to use a phrase such as 'twice a week' or 'every two years'.

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