I. (ˌ)bī-ˈmən(t)th-lē adjective
Date: 1845
1. : occurring every two months
2. : occurring twice a month : semimonthly
Usage: see bi-
II. adverb
Date: 1858
1. : once every two months
2. : twice a month
III. noun
Date: circa 1890
: a bimonthly publication