A swap that has exotic or complex structure whereby it is distinguished in its key underlying economic variables from basic swaps. Irregular swaps have generic and proprietary (trademark) names. Examples of generic-name swaps include amortizing swaps, cancellable swaps, binary accrual swaps, etc. Proprietary names for swaps are usually given by dealers and institutional investors to trademark their products. A 5/30 swap and a LIBOR-squared swap are examples of proprietary swaps.

An irregular swap (also an exotic swap or a flavored swap) is the opposite of a vanilla or plain vanilla swap.