kneecap

• POS: Noun, Verb (usu participle), Verb (transitive)
• HYPHEN: knee=cap

CIDE DICTIONARY

kneecap, n. 

•  A roundish, flattened, sesamoid bone in the tendon in front of the knee joint; the patella; the kneepan.  [1913 Webster]
•  A cap or protection for the knee.

kneecap, v. t. 

 to break the knees of, especially by shooting in the kneecap; -- often done by criminal or terrorist groups as a warning or punishment.
""  [WordNet 1.5]

OXFORD DICTIONARY

kneecap, n. & v.
--n.
1 the convex bone in front of the knee-joint.
2 a protective covering for the knee.
--v.tr. (-capped, -capping) colloq. shoot (a person) in the knee or leg as a punishment, esp. for betraying a terrorist group.

Derivative

kneecapping n.