underthigh

Noun

 * 1) The back of a person's thigh.
 * 2) * 1883, Albert Ellery Berg (ed.), The Universal Self-Instructor, New York: Thomas Kelly, “Out-Door Exercises,” p.350,
 * You may walk so as to use neither calf, under-thigh, nor hip to any appreciable extent; but it is hard work to run in any way so as not to develop all three
 * 1) The back upper portion of a pantleg or trouser leg.
 * 1) The back upper portion of a pantleg or trouser leg.
 * 1) The back upper portion of a pantleg or trouser leg.
 * 1) The back upper portion of a pantleg or trouser leg.