This word is in the language, but I'm still meeting people who don't know what it means. So, let's have a look: It originates in German chess terminology, where it describes a situation in which a player has to make a move (one cannot "pass" in chess), but all legal moves available will make his/her position worse. The word combines
Zug ("move" in the context of board games) and
Zwang ("compulsion", "being forced to do something").
Zugzwang is now generally used to indicate this sort of dilemma, and this makes it a very useful addition to one's vocabulary.
Note on pronunciation: Tsook-tsvang, where the "oo" is long, as in "fool", and the "a" is open like in "father", not like in "gang".