zero-day.

1. A software vulnerability newly discovered or previously unknown to those responsible for addressing it, commonly before an effective fix is available.

2. An exploit or attack that takes advantage of a zero-day vulnerability before an effective fix is available.

Use it for

Words that belong together

• a zero-day vulnerability
• discover a zero-day

On the page

The security report described a zero-day vulnerability in the communications software.

The crew isolated the affected terminal after discovering the zero-day.

Usage notes

Primary category: sci-fi. Forms: Singular zero-day; plural zero-days. Legacy lexical fields mirror sense 1 only. Use numbered sense fields for all meanings.