Definition

RACI stands for:

• Responsible — this is the person responsible for completing tasks or deliverables, and making sure the project gets shipped at the highest level. Decisions can be escalated to them.
• Accountable — this person is the project owner or project manager and has final responsibility and decision making for the correct completion of project tasks. They're doing the everyday planning, assigning tasks, and ensuring that what’s supposed to happen, happens. Usually, there's only one of these people on the matrix. Sometimes the same person is both the R and the A.
• Consulted — think of these folks as those who need to be in the loop or provide feedback on deliverables or asked for advice in advance of performing tasks.
• Informed — this person isn't directly responsible for any work. Instead, they should be given updates about big decisions or progress. No response or action expected.

Resources

The Secret to a Successful RACI Matrix