Merriam-Webster Collegiate Dictionary - fusee

 noun  Etymology: French fusee, literally, spindleful of yarn, from Old French, from fus spindle, from Latin fusus  Date: 1622  1. a conical spirally grooved pulley in a timepiece from which a cord or chain unwinds onto a cylinder containing the mainspring and which by its increasing diameter compensates for the lessening power of the spring  2. a red signal flare used especially for protecting stalled trains and trucks