Dilemma

A dilemma is a problem offering two (or more) solutions, neither of which is acceptable. The two options are often described as the horns of a dilemma, neither of which is comfortable.

The dilemma is sometimes used as a rhetorical device, in the form "you must accept either A, or B"; here A and B would be propositions each leading to some further conclusion. Applied in this way, it may be a fallacy.