When one person (typically the follower) turns, and this movement is amortized by a counter movement by the other person (leader), so the first person slows down, stops and maybe even starts turning the other way.
The timing of the countermovement is key, it should be some time before the original movement is supposed to stop. Think 'elastic' or 'jo-jo' effect.
If a woman is rotating, say, clockwise on her own axis, and the man starts gravitating around her counter-clockwise, and if in addition there is a properly toned frame connecting the two, at some point something's gotta give, and of course it will not be Mr. Macho Man. The woman's movement stops.
(from Tango-L (http://pythia.uoregon.edu/~llynch/Tango-L/2000/Aug/Aug-31-to-Sep-01.html))