Source : Webster's Revised Unabridged Dictionary (1913)

Hamstring \Ham"string`\, n. (Anat.)
   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.

Hamstring \Ham"string`\, v. t. [imp. & p. p. {Hamstrung}; p. pr.
   & vb. n. {Hamstringing}. See {String}.]
   To lame or disable by cutting the tendons of the ham or knee;
   to hough; hence, to cripple; to incapacitate; to disable.

         So have they hamstrung the valor of the subject by
         seeking to effeminate us all at home.    --Milton.

Source : WordNet®

hamstring
     n : one of the tendons at the back of the knee [syn: {hamstring
         tendon}]
     [also: {hamstrung}]

hamstring
     v 1: make ineffective or powerless; "The teachers were hamstrung
          by the overly rigid schedules"
     2: cripple by cutting the hamstring
     [also: {hamstrung}]