linguistic descriptivism is correct 99% of the time but for the word "biweekly" specifically the world would be tangibly better if a cabal of dictionary authors just arbitrarily chose one of the widely used meanings to deem correct
i collect words like this, with two incompatible and ideally opposite definitions! i also have “sanctioned” and “unlockable”
Contranyms! My favorite is probably "oversight", because it makes me giggle every time I hear about an "oversight committee"
My brain's got a whole frickin oversight committee