absurdly

adverb

that is an absurdly optimistic claim:

preposterously, ridiculously, ludicrously, farcically, laughably, risibly;

idiotically, stupidly, foolishly, inanely, insanely, madly, wildly, fantastically, grotesquely;

completely, absolutely, entirely, totally, wholly, thoroughly, utterly, beyond, quite, altogether, downright, perfectly;

unbelievably, incredibly, unthinkably, implausibly;

extremely, exceedingly, excessively, exorbitantly, unduly, inordinately, immoderately, unreasonably, irrationally, illogically, impossibly;

offensively, unspeakably, intolerably, maddeningly, outrageously, shockingly;

informal crazily, barmily.

▷antonyms reasonably, sensibly; somewhat.

absurdly Oxford Dictionary of English