Battle cries were sayings used as motivation when facing a difficult situation.
Kahless the Unforgettable was said to have the battle cry "Today is a good day to die." (VOY: "Dragon's Teeth")
Another old Klingon battle cry spawned the favorite saying of Lyndsay Ballard, "Own the day." (VOY: "Ashes to Ashes")
In 2372, Kor told a story of Koloth chanting a battle cry as he attacked the flanks of T'nag's army with Kang and Kor. (DS9: "The Sword of Kahless")