Esoteric Debt

The Finnegans Wake of debt. That is, debt that's hard to understand.

Esoteric debt instruments are ones that have a significantly complex structure. Weird derivatives. Swaps and swaptions. Strange forms of foreign currency which trigger sudden payoffs. Because of this gnarliness, most people can't (or at least don't want to bother to) understand them. This fact makes the debt difficult to price and difficult to sell (meaning they are not very liquid).