Occurring every two months, or (less commonly) occurring twice within one month; a publication issued bimonthly.
From bi- (two) + monthly. The ambiguity arose because bi- can mean both 'every two' and 'two times,' creating confusion that has persisted since the term's emergence in English.
Linguists actually call bimonthly an 'autantonym'—a word that means its own opposite! The only way to be clear is to say 'every other month' or 'twice monthly' instead.
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