1. A state of open, often prolonged fighting; a battle or war.
2. A state of disharmony between incompatible or antithetical persons, ideas, or interests; a clash.
3. Psychology A psychic struggle, often unconscious, resulting from the opposition or simultaneous functioning of mutually exclusive impulses, desires, or tendencies.
4. Opposition between characters or forces in a work of drama or fiction, especially opposition that motivates or shapes the action of the plot.

1. To be in or come into opposition; differ.
2. Archaic To engage in warfare.

Synonyms: These nouns denote struggle between opposing forces for victory or supremacy. Conflict applies both to open fighting between hostile groups and to a struggle between antithetical forces: "The kind of victory MacArthur had in mind . . . victory by expanding the conflict to all of China—would have been the wrong kind of victory" (Harry S. Truman). "Fortunately analysis is not the only way to resolve inner conflicts" (Karen Horney).
Contest can refer either to friendly competition or to a hostile struggle to achieve an objective: a spelling contest; the gubernatorial contest.
Combat most commonly implies an encounter between two armed persons or groups: "Alexander had appeared to him, armed for combat" (Connop Thirlwall).
Fight usually refers to a clash involving individual adversaries: A fight was scheduled between the world boxing champion and the challenger. "There is nothing I love as much as a good fight" (Franklin D. Roosevelt). See Also Synonyms at discord.