Kunoichi refers to a female ninja or practitioner of ninjutsu(And by ninjutsu I don't mean the ninjutsu shown in Naruto.).
Female ninja played a big role in the history of Ninjutsu. They were assigned tasks that could not be completed by men. They would often use their charm to enter areas without raising suspicion, gather information, and if necessarily, kill their target.
The kunoichi training was different than ninja training. It focused more on stealth, strategy, small weapons, poisons and explosives and less on larger weapons like swords and spears. Also kunoichi were though the arts of singing, dancing, musical instruments and the tea ceremony so that they would be able to get close to their victim without being suspicious.
K has so far been the hardest letter, so this post is a bit lame. My N post will be about ninjutsu and I will try to make it more interesting that this.