Here is the list of all the English words whose definition contains "OS" containing letters A, B, C, D, E, F, I, L, N, O, P, R, S and T not containing letters A, B, C, E, H, I, L, M, N, O, P, Q, S, T and U grouped by number of letters:
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Please note: the Wiktionary contains many more words - in particular proper nouns and inflected forms: plurals of nouns and past tense of verbs - than other English language dictionaries such as the Official Scrabble Players Dictionary (OSPD) from Merriam-Webster, the Official Tournament and Club Word List (OTCWL / OWL / TWL) from the National Scrabble Association, and the Collins Scrabble Words used in the UK (about 180,000 words each). LotsOfWords knows 480,000 words.