What term describes the obstruction of an opponent by contacting him with any part of a blocker’s body?

The term that describes the obstruction of an opponent by contacting them with any part of a blocker’s body is "block." In football, blocking is a fundamental technique used by offensive players to protect the ball carrier or to create space during a play. Proper blocking involves making contact with the opponent while adhering to specific rules regarding player safety and legal methods of contact.

In contrast, a "foul" refers to a violation of the rules, often resulting in a penalty. A "tackle" specifically describes the act of bringing down the ball carrier to stop their progress. A "penalty" is a consequence of a foul, which leads to a loss of yardage or an advantage for the opposing team. The focus of the question is on the act of blocking itself, which is an essential tactic in the game, making "block" the correct term for the scenario described.