Definitions of tackle:

• noun:   (American football) grasping an opposing player with the intention of stopping by throwing to the ground
• noun:   a position on the line of scrimmage

  Example: "It takes a big man to play tackle"

• noun:   the person who plays that position on a football team

  Example: "The right tackle is a straight A student"

• noun:   gear used in fishing
• noun:   gear consisting of ropes etc. supporting a ship's masts and sails
• verb:   seize and throw down an opponent player, who usually carries the ball
• verb:   accept as a challenge

  Example: "I'll tackle this difficult task"

• verb:   put a harness