resembling a nightmare, especially in being terrifying, exasperating, or the like: his nightmarish experience in a concentration camp.

Origin of nightmarish

First recorded in 1825–35; nightmare + -ish1
Related formsnight·mar·ish·ly, adverbnight·mar·ish·ness, noun Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for nightmarish

Contemporary Examples of nightmarish

Historical Examples of nightmarish

Word Origin and History for nightmarish

1834, from nightmare + -ish. Related: Nightmarishly; nightmarishness.

Online Etymology Dictionary, © 2010 Douglas Harper