night·mare 
/ˈnaɪtˌmeɚ/ noun
plural night·mares /ˈnaɪtˌmeɚ/ noun [count] 1 : a dream that frightens a sleeping person : a very bad dream
▪ Mommy, I had a really scary nightmare. ▪ She had a recurring nightmare [=she had the same bad dream many times] about losing her job. 2 : a very bad or frightening experience or situation
▪ The party was a complete nightmare. ▪ a nightmare situation/scenario ▪ Losing a child is every parent's worst nightmare. [=the thing every parent fears most]
▪ Mommy, I had a really scary nightmare. ▪ She had a recurring nightmare [=she had the same bad dream many times] about losing her job.
▪ The party was a complete nightmare. ▪ a nightmare situation/scenario ▪ Losing a child is every parent's worst nightmare. [=the thing every parent fears most]
— night·mar·ish /ˈnaɪtˌmerɪʃ/ adjective [more nightmarish; most nightmarish]
▪ a nightmarish experience
/ˈnaɪtˌmerɪʃ/ adjective [more nightmarish; most nightmarish] ▪ a nightmarish experience
