Definition

From horse racing; a man who walks the horses but is never allowed to mount them: In tango it refers to a man who dances and flirts with all the ladies but never gets involved with anyone. May also refer to a man who is a clumsy or inconsiderate lead who "might just as well be walking a horse."

(from tangoafficionado.com (http://www.tangoafficionado.com/tango_terminology.htm))