noun

• (anatomy) One of the great tendons situated in each side of the ham, or space back of the knee, and connected with the muscles of the back of the thigh.
• (informal) The biceps femoris, semimembranosus, and semitendinosus muscles.
  "Developing muscle around both sides of a joint (think biceps and triceps, abs and low back, quads and hamstrings) should be one of your primary training considerations because strength on each side leads to lower injury rates."

verb

• (transitive) To lame or disable by cutting the tendons of the ham or knee; to hough.
• (transitive, figurative) To cripple; to incapacitate; to disable.
  "So have they hamstrung the valor of the subject by seeking to effeminate us all at home."