I usually say “semiweekly” to mean twice per week. I also say “semimonthly” to mean twice per month (24 times per year) as opposed to “biweekly” (26 times per year).

The fact that American English doesn't have the word 'fortnightly' is incredibly confusing on every level.

This is the only word I know of whose meaning can be redefined by majority consensus.

Case in point, my workplace wanted a bi-weekly committee meeting for our team to work on stuff over a zoom call. I asked what days these meetings would be held and they all agreed "Just Thursdays". When I tried to argue that a bi-weekly meeting necessarily means that there must be two distinct dates per week, they all agreed that bi-weekly obviously means every other Thursday and that I didn't understand what the word bi-weekly meant 😒

Biweekly is every two weeks (fortnightly)

Semi-weekly is twice a week.

Same rule as bimonthly and semimonthly.