To boost means to push something upward or make it stronger, bigger, or better. When you boost your friend over a fence, you're giving them a lift from below. When a rocket engine provides extra boost during liftoff, it supplies additional power to push the spacecraft higher and faster.

The word often describes increasing or improving something that already exists. A student might boost their grade by studying extra hard for the final exam. A company might boost sales by offering a special discount. Exercise can boost your energy levels, and a good night's sleep can boost your immune system. Scientists working on a vaccine look for ways to boost the body's natural defenses against disease.

Boost can also mean to support or encourage. When you boost someone's confidence, you help them feel more sure of themselves. When friends boost each other's spirits before a big game, they're building each other up with encouragement.

That original sense of lifting upward still colors how we use it: whether you're boosting a physical object, a number, or someone's mood, you're always pushing it higher than it was before.

As a noun, a boost is the extra lift, power, or improvement itself.