das Unwesen
Translation
mischief, nuisance, havoc, nefarious activities
Examples
Die Diebe trieben in der Stadt ihr Unwesen.
The thieves were up to their mischief in the city.
Ein Geist soll hier sein Unwesen treiben.
A ghost is said to be causing trouble here.
Grammar Patterns
sein Unwesen treiben to be up to no good, to wreak havoc A gang of youths was wreaking havoc in the park.
Similar Words
Synonyms: der Unfug (mischief), das Treiben (doings), der Spuk (haunting)
Etymology
From Un- (a prefix indicating something bad or wrong) + Wesen (a being, creature, essence). So, a 'bad being' or 'bad activity'.
Memory Tips
Almost always used in the fixed phrase 'sein Unwesen treiben' (to be up to no good, to wreak havoc). Picture a mischievous 'un-being' causing trouble.