noun
female ninja; kunoichi
Refers specifically to a female ninja in historical or fictional contexts. The term is derived from the strokes of the kanji 女.
くノ一は忍術を使って敵を欺いた。
The kunoichi used ninjutsu to deceive the enemy.
Colloquial, often playful or slangy way to refer to a woman, derived from the ninja term.
あのくノ一はなかなか手ごわい。
That woman is pretty tough.
The term is said to derive from the three strokes of the kanji 女 (woman): く, ノ, and 一, which together form the character. The exact historical origin is uncertain, but it is widely used in popular culture to refer to female ninjas.