In Latin, it means a “manner of living”, or a “way of life”. In English, however, the expression is not used to mean this. It is used to refer to a compromise, usually temporary, between two parties that are fighting each other. One often hears this expression used by foreign ministers. If someone in the foreign ministry were to say, “If India and Pakistan want to avoid a nuclear holocaust, a modus vivendi must be attained,” what he means is that despite the many differences, the two countries must find a way of coexisting peacefully.
*The two rival gangs managed to achieve a sort of modus vivendi.