What is the word for letters that do not ascend above the midline / uniform height? (i.e. aceuomnwxz, not btlj)

Solution 1:

I think you could call them x-height letters. From Wikipedia:

Lowercase letters whose total height is greater than the x-height either have descenders which extend below the baseline, such as y, g, q, and p, or have ascenders which extend above the x-height, such as l, k, b, and d.

We can infer that letters which do not have descenders or ascenders are (approximately) x-height. (If you want to be picky, an "x" is not always the exact same height as an "s," but it's generally close enough.)

Which letters have ascenders and descenders may depend on the typeface or script variant that is being used. But in normal modern Latin fonts, I believe the set of letters with neither ascenders nor descenders is consistent.

Solution 2:

Running the string weruoaszxcvnm past a Scrabble word generator produces the nine-letter word cavernous.

I imagine there are longer technical words.

Editing later to add: my previous answer assumed that each letter could be used only once. If you can use any of these letters any number of times the problem gets out of hand. Doubling up the string twice and then having a stab at adding in a few more of what I judged "useful" ones turned up curvaceousness at 14 letters. I'd also like to point out that necromancer is the longest word if every letter is only allowed twice because, come on, necromancer, dude.

Editing yet again because we missed "i": In this case the longest word with only one use of each letter is microwaves at 10, allowing them twice gets you a tie at 13 with unceremonious and anniversaries. Chucking in one more letter (because that's the longest string I could handle) got me up to 15 with overanxiousness, carnivorousness, and the smacks-of-cheating unveraciousness.