HoughmagandyAlso spelled "houghmagandie" or "houghmangandy". The definition is to engage in "relations" with someone who is not your spouse.
One well-known appearance is in Vladimir Nabokov’s book Pale Fire: “She would have preferred him to have gone through a bit of wholesome houghmagandy with the wench”.
The word is Scottish in origin - as the guttural "gh" indicates. The first part is the same word as "hock", the joint in a four-legged animal that matches the human ankle, sometimes still spelled that way (as in the Scottish hough soup).
The second element of the word is uncertain. It could be from "canty", a Scottish and northern English dialect adjective for someone who is lively or cheerful, or perhaps active or brisk. So, a bit of active thigh work — you can see how the word could have arisen.
There seems to be no link with the similar-sounding but obsolete Australian word for a thin and unpalatable stew, "hashmagandy". Best not to get these two words confused...