Zorro is a made-up hero from American books, films and television. He is a rich gentleman in old Spanish California who leads a second, secret life: at night he puts on black clothes, a black cape and a black mask over his eyes, rides a black horse, and fights cruel officials to protect ordinary people. His trademark is his sword — he cuts a sharp letter Z into a wall, a door, or the clothes of a man he has beaten, so everyone knows who was there. He first appeared in a story in 1919 and has been played by many actors since; in Taiwan he has long been known as 蘇洛 or 黑俠蘇洛.

Because the character is so well known, the name gets used loosely for two things: a person who does secret good deeds while hiding who they are, and, more often, the mask itself — a 'Zorro mask' is that thin black strip across the eyes. People also joke about 'signing your name like Zorro' when someone makes a big showy Z-shaped scribble. Capital letter, no 'the'. In Spanish the word means 'fox', which is exactly the point: quick, clever, hard to catch.