Arrant1. (a.) Notoriously or thoroughly bad; thorough or downright, in a bad sense; shameless; unmitigated; as, an arrant rogue or coward.
2. (a.) Thorough or downright, in a good sense.
Thesaurus Entries
abject, abominable, absolute, atrocious, awful, bad, barefaced, base, beastly, beggarly, beneath contempt, black, blamable, blameworthy, blatant, bold, brassy, brazen, brazenfaced, brutal, cheesy, classical, complete, conspicuous, consummate, contemptible, crass, criminal, crummy, damnable, dark, debased, decided, definitive, degraded, deplorable, depraved, despicable, detestable, dire, dirty, disgraceful, disgusting, downright, dreadful, egregious, enormous, evil, execrable, fetid, filthy, flagitious, flagrant, flat-out, foul, fulsome, glaring, grave, grievous, gross, hanging out, hateful, heinous, horrible, horrid, improper, impudent, in relief, in the foreground, infamous, infernal, iniquitous, intolerable, knavish, lamentable, little, loathsome, lousy, low, low-down, lumpen, mangy, mean, measly, miserable, monstrous, nasty, naughty, nefarious, noisome, notable, noticeable, notorious, obnoxious, obtrusive, odious, offensive, ostensible, out-and-out, outrageous, outright, outstanding, overbold, paltry, peccant, perfect, petty, pitiable, pitiful, plain, poky, poor, positive, precious, profound, prominent, pronounced, proper, pure, rank, regrettable, regular, reprehensible, reprobate, reptilian, repulsive, rotten, sad, salient, scabby, scandalous, schlock, scrubby, scruffy, scummy, scurvy, shabby, shameful, shattering, sheer, shocking, shoddy, sinful, small, sordid, squalid, staring, stark, stark-staring, sticking out, striking, superlative, surpassing, terrible, the veriest, thorough, thoroughgoing, too bad, total, unabashed, unbearable, unblushing, unclean, unconscionable, undeniable, unequivocal, unforgivable, unmentionable, unmitigated, unpardonable, unqualified, unrelieved, unspeakable, unspoiled, unworthy, utter, vicious, vile, villainous, wicked, woeful, worst, worthless, wretched, wrong