Dancing without keeping the feet on the floor. This was the style before the turn of century when tango was danced on dirt surfaces in the patios of tenements, low-class taverns, and on the cobble stone streets. Once tango went uptown enough to actually be danced on floors (wood, tile, or marble) the dancers fell in love with the floor, thus we now refer to 'caressing the floor'. Characteristic of canyengue or orillero-style tango.
(from tejastango.com (http://www.tejastango.com/terminology.html#E))