ham·string / ˈhamˌstring/ • n. any of five tendons at the back of a person's knee: he pulled a hamstring. ∎ the great tendon at the back of a quadruped's hock.• v. (past and past part. -strung) [tr.] cripple (a person or animal) by cutting their hamstrings. ∎ (usu. be hamstrung) severely restrict the efficiency or effectiveness of: we were hamstrung by a total lack of knowledge.