bad trip
n., slang, also used colloquially A disturbing or frightening experience, such as terrifying hallucinations, while under the influence of drugs; hence, by colloquial extension any bad experience in general.
Why's John's face so distorted?
■ He had a bad trip.
How was your math exam?
■ Don't mention it; it was a bad trip.

[TahlilGaran] English Idioms Dictionary ▲