Meaning

• A six-point score occurring when the ball enters possession of a team's player in the opponent's end zone.

  "Today I scored my first touchdown."

• A defensive action of grounding the ball in the team’s own in-goal to stop the play

• A try (scoring play of grounding the ball in the opposing team’s in-goal)

• The moment when an aircraft or spacecraft makes first or final contact with the ground during a landing.

  "The passengers audibly relaxed at touchdown."

• The moment of contact of a tornado with the ground.