Bus Factor
Noun · Hacker Culture
Definitions
The minimum number of team members who would need to be suddenly unavailable (hit by a bus, quit, go on vacation) before a project stalls due to loss of critical knowledge. A bus factor of 1 means a single departure could cripple the project.
In plain English: How many people could leave your team before nobody knows how to keep the project going.
Example: "Our bus factor on the billing system is 1 — only Sarah understands the invoice reconciliation code. We need to fix that."