Block

1. To prevent (something) so that it is not possible (or to prevent) to pass. A large boulder blocked the road.
2. (sports) An action to interfere with the movement of an opposing player or of the object of play (ball, puck). In football some player block the opposing players.
3. Something that prevents something from passing. There is a block in the pipe that prevents the water from flowing.
4. A set of like items, such as a shares of stock, sold as a unit. They bought a large block of IBM shares that day.