Unilateralism is any doctrine or agenda that supports one-sided action. Such action may be in disregard for other parties, or as an expression of a commitment toward a direction which other parties may find agreeable.
Unilateralism is a
neologism which is already in common use; it was coined to be an
antonym for
multilateralism, which is the doctrine which asserts the benefits of participation from as many parties as possible.