turn, rotation or bend
The giro is the manoeuvre in which the follower, always facing the leader with her upper body, is led to step around her leader - progressively taking backward, open/side, and forward steps before pivotting 180 into another open/side step and pivotting 180 and repeating the backward, open/side and forward steps and so on.
The move can include any number of the individual elements and can begin and end on any step although there are favoured entry and exit points and variations on the timing of the steps.
(from layuega.com (http://www.layuega.com/giros.htm))
The Giro is an important figure in which the lady circles the man who stays in position and turns by means of a series of pivots. The Giro can be made to the left or right (... step description)
(from tangohk.com (http://tangohk.com/learn_tango_p5.htm))
Apparently there is some confusion over these words, where some dancers note their teachers from Argentina have never used the word molinete (Juan Rando) and use just the word giro or other similar words such as vuelta.
(from tangocanberra.asn.au (http://www.tangocanberra.asn.au/words.htm#Giro))