What does it mean when abs light stays on in a vauxhall?

Anti-lock Braking System Warning Light

Usually, that means that there is something wrong, somewhere, in the Anti-lock Brake system.

Someone has to "troubleshoot" the system to determine what the fault is that's causing the light to stay on. It could be anything, including a defect in the warning wiring itself, but usually means there is something wrong with the braking system.

Get it checked out by a QUALIFIED automotive brake tech or mechanic.