What is retrograde sweep second in a wrist watch?

Answer 1

http://culture.hautehorlogerie.org/en/encyclopaedia/complication-watches/complications-by-concept-and-production/retrograde-hours-and-other-retrograde-indications-544.html

A retrograde hand on a watch sweeps through part of a circle and then springs back to the beginning and repeats. It doesn't go all the way around the dial.