To cancel out something means doing something that take away the effect of something else.
Example sentences:
- Ryanair ticket prices may look cheap at first glance. But they don't include airport taxes and other fees that may cancel out the apparent cost advantage of flying with Ryanair.
- Our company had great two first quarters. But the profits were mostly canceled out by losses in the last two.
- Noise canceling headphones work by generating a soundwave that cancels the noise out.