There are circumstances where a word that is not in any dictionary can be acceptable in Chihuahua. One such circumstance is where the word is the product of a recognised construction rule. I think this is the case with
sevenish and similar words.
The Shorter Oxford's entry for the suffix
-ish includes this:
(d) colloq. from names of hours of the day or numbers of years, w. the sense 'round about, somewhere near (the time or period of)', as elevenish, fortyish.
Other dictionaries have similar descriptions, some giving
sevenish as an example. So I think
sevenish is definitely accepted by the dictionaries as a word, even though none of them seems to have an actual entry for it. And it certainly is in fairly frequent use, in books as well as in conversation.
So I think
sevenish should be allowed, birdy, but this raises the question: what about
sixish,
eightish and all the other "[number]ish" words? If I'm going to allow one of the words in this category, I feel all of them should be admitted. It would be too confusing otherwise. Fortunately, we don't have to worry about compound words or words longer than nine letters, so it's basically most of the numbers from
oneish to
twelvish, and most of the multiples of ten from
twentyish to
ninetyish. (Quite a few of these will probably never come up in a puzzle, but I would like to include them all in the word list for consistency.)
With regard to the general topic of
-ish words, that RM raises, I think I'll leave that can of worms for another day.