Unless I am trying to be funny and the ambiguity of the words I choose is desirable for the humor, I try not to use ambiguous language at all.
Does anybody else...?
The place for asking whether anybody else does the same stupid stuff like you do
There are not two definitions. The prefix (bi) modifies the root (week). The suffix (ly) modifies the combination (biweek). Biweekly will always mean "once every two weeks" due to the order in which English dictates that the modifiers operate.
Man I wish English wasn't known for having many, many exceptions to every rule. Then you might have had a chance to be correct and communication wouldn't confuse so many autistic people.
The team I was on at work number of years ago had to hash this exact thing out because we had a "biweekly" status and was confusing people. We ultimately landed on not using the term.
Bimonthly and biannually have the same problem.
Biannual does not because of biennial.
Biannual: two times per every one year
Biennial: one time per every two years
No idea if there's similar words for weekly/monthly but I only know about yearly from this https://youtu.be/ljkaN_-d-Zg
The Archer clip is wrong. Webster literally lists biennial as a definition for biannual, along with twice a year.
https://www.merriam-webster.com/dictionary/biannual
Cambridge says the same:
https://dictionary.cambridge.org/dictionary/english/biannual
Oxford put their stuff behind a paywall.