It estimated 74k words for me, but I feel this might be inflated; much of the time when I didn't know the answer - I could vibe guess it just as you did it. The distractor answers weren't convincing enough. For starters, when an answer was based on deconstructing the word into common English words, that ruled it out. After all, if it was, then it wouldn't have been obscure.

A tangent: writing distractors for multiple choice questions is hard. From the exams I know (excluding those whose nature precludes it, such as based on calculation or rote memorization) the only that does this brutally well is LEK (Polish medical graduate exam). It's nigh impossible to vibe guess it at more than random chance for someone outside the field.

What I also noticed: when there are two contradictory definitions to choose from, it is usually one of those two.

For all its shortcomings, this was part of the fun, deducing the likely correct answer when you see a word for the first time.

Yeah I also got exactly 74k. Stuff like “xylologist” I guessed had to do with vegetation because of “xylem”, whereas xylophone player was too on the nose. Then again, maybe knowing xylem in the first place makes 74k reasonable.

in casual use you might also be able to guess it from context, so i think it’s a wash

Indeed. "Lethargic" meaning "affected by lethargy" would hardly be difficult to guess!

> A tangent: writing distractors for multiple choice questions is hard.

In case of online quiz you can have a "competition" between distractors:

1. start by having much more distractors than needed and pick randomly

2. for each measure the probability of it getting clicked (clicks/times it's shown)

3. show the most frequently clicked distractors more often

It would have been nice to have an “i don’t know” button. Instead I decided to select the first option for words I didn’t know instead of trying to figure them out. Although when I got to the final group I couldn’t resist trying to figure them out. It estimated 61k for me.