"Antidisestablishmentarianism" (28 letters) is the longest non-coined, non-technical word in the English language, and refers to the doctrine opposing the removal of state support for an established Church, which in the original usage was the English Anglican Church.
The longest English word that appears in dictionaries (although labeled as factitious) is pneumonoultramicroscopicsilicovolcanoconiosis (45 letters)
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Evidently you are trying to spell the longest "real" word in the English language. It is spelt "antidisestablishmentarianism".
electric
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Using all of the letters you can spell the words "issuant" and "sustain".
The longest common word is "luminous" (8 of the 12 letters).
There is no anagram to OPOADSE. The longest word is "soaped."(The letters IPOADSE spell the word adipose.)
The longest word in the English Language is Pneumonoultramicroscophicsilicovolcanoconiosis
The letters 'llarach' cannot be unscrambled to spell a single word. The longest possible word is halal.
The letters 'sabronia' unscramble to spell the word abrasion. The next possible longest word is abrosia.
The letters 'bpumtsif' cannot be unscrambled to spell a single word. The longest possible word is submit.
There is no anagram. They do spell the word pairs "fair rap" and "fair par." The longest word is "friar."
There is no one-word anagram. You can spell the word pair "our side." The longest words are roused and soured.