well, that at least makes me feel better about preferring to use it to mean twice a month, as my coworker was rather annoyingly superior about her insistence that semi-monthly was the only right option. She had this "oh, you're always so contrary and I'll humor you even though I know the correct answer" vibe that bugged the heck out of me.
I think it's fair to say that
semimonthly is the only
unambiguous option, but everything beyond that is just, like, people's opinions, man.
I guess I've gotten lucky? Or always clarified when it mattered because I was aware there was confusion. But how useless! What is the point to it if one always has to clarify it? And when we already have "semi" when we want to say twice a whatever?
It's often clear from context, like when a bimonthly newsletter comes out in January, March, May, and so on.
It looks like these uses of
bi- and
semi- arose around the same time, and often when that happens, it's not really planned—people are just trying to fill a need. And so someone trying to communicate "twice a month" might say "bimonthly" because it seems to make sense in context, while someone else trying to communicate "every two months" says the same thing because it also makes sense in context.
I'm not sure if
bi- was ambiguous in this way in Latin, but it's been used that way in English so long that there's really no going back now.