Source : Webster's Revised Unabridged Dictionary (1913)

Bimonthly \Bi*month"ly\, a. [Pref. bi- + monthly.]
   Occurring, done, or coming, once in two months; as, bimonthly
   visits; bimonthly publications. -- n. A bimonthly
   publication.

Bimonthly \Bi*month"ly\, adv.
   Once in two months.

Source : WordNet®

bimonthly
     adj 1: occurring twice a month; "a semimonthly publication" [syn: {semimonthly}]
     2: occurring every two months; "bimonthly visits" [syn: {bimestrial}]
     n : a periodical that is published bimonthly
     adv 1: twice a month; "salaries are paid semimonthly" [syn: {semimonthly}]
     2: every two months; "the bill was payable bimonthly"