Thrustle

[Sarah]

The throstle, or song thrust. [Obs. or Prov. Eng.]When he heard the thrustel sing. Chaucer.

[Sarah]

Muscle in humanoids loosely defined as the part of the body located between the mid thorax and the mid thigh. Used primarily for thrusting, typically during intercourse although not always (for example it is possible to propel oneself around a room on a wheeled object by using only the thrustle, without contact with the floor by feet or hands).