"A fighting ko involves repetitive removal; immediate removal of hot stones is prohibited. A disturbing ko involves cyclic removal; the disturber is prohibited from recycling."
"When life and death are settled, recycling of interchangable breaths is called a disturbing ko. The player who starts a disturbing ko is called the disturber. By attacking his opponent or using a double ko, the disturber creates a disturbing ko with no hot stones. After one cycle, the disturber is never allowed to continue disturbing."
Taken from Ing's Wei-ch'i Rules.