📒 a rocket that gives a spacecraft extra power when it leaves the earth, or that makes a missile go further
📒 a device that gives extra power to a piece of electrical equipment
📒 an extra small amount of a vaccine that is given to increase the effect of one given earlier, for example to protect you from a disease for longer
📒 a thing that helps, encourages or improves somebody/something
📒 a person who gives their support to somebody/something, especially in politics