Definitions of keen:

• noun:   a funeral lament sung with loud wailing
• verb:   express grief verbally
• adjective:   having a sharp cutting edge or point

  Example: "A keen blade"

• adjective:   very penetrating and clear and sharp in operation

  Example: "A keen intelligence"

• adjective:   intense or sharp
• adjective:   as physically painful as if caused by a sharp instrument

  Example: "Keen winds"

• adjective:   having or demonstrating ability to recognize or draw fine distinctions
• adjective:   very good
• name:  A surname (common: 1 in 12500 families; popularity rank in the U.S.: #1624)