The word "thighbone" refers to the femur, the longest and strongest bone in the human body. However, there are several synonyms for this bone, including the thigh bone, the femoral bone, and the os femoris. Other synonyms include the upper leg bone, the femoral shaft, and the femur bone. These terms are often used interchangeably to describe the structure that connects the hip to the knee. Additionally, medical professionals may also use technical terms such as the diaphysis of the femur or the proximal end of the femur to refer to this bone.