A stiletto is a short dagger, with a narrow, hollow grind blade with a triangular cross-section. This dagger is designed as a stabbing weapon rather than for cutting, since it doesn't have a sharp edge, and because its narrow shape allows it to penetrate deeply in a point.
The stiletto began to gain fame during the Renaissance when it was popular as a tool against heavily armoured knights. The thin blade could easily pass through most chainmail, or find its way through tiny gaps in a knight's armour.
The stiletto was also favoured amongst assassins because it was an easily concealed weapon. This tactic occurred repeatedly, from the Zealots of 1st century Judaea, to the Venetians and the Assassins of Alamut.
The word stiletto may sometimes be used in American English to refer to a switchblade.