From Unofficial BOINC Wiki
The end state of the analysis for the specific Result.
A Result in this state was processed successfully and there were no errors detected by the BOINC Client Software and the Science Application on the Participant's Computer. This does not mean that the Result is scientifically valid or meaningful. It is entirely possible that the Result is "bad" and when compared to other Results will not achieve consensus and the Work Unit will be rejected because it exceeds the Max success results limit.
The Result was issued and the Participant's Computer returned an error during processing of this Result. There are a number of Client Error conditions that can occur and that can be detected by the BOINC Client Software and recorded.
The Result was issued to a Participantt and the Result was not returned within the time specified by the Deadline. This error may occur due to problems in the data transfers, processing, or simply because the Participant's Computer was not able to complete the processing within the time allotted.
The Result was not sent out at all, either due to already had enough Results returned by other Participants and a Quorum of Results was created before this Result was issued to someone, or the Work Unit was aborted. Most commonly, these aborts are due to the Work Unit reaching one of the error-limits before this Result was issued to someone.
The Result was reported but could not be Validated. This error, most typically, is because the Result Data Files were lost on the Data Server. Other causes include Result Data Files, or the Result itself was not correctly received usually due to data transfer errors or heavy server loads.
Note: A Result Outcome of "Validate Error" is not the same as a Valid Result. See Validate State for an explanation of the various types of Validation outcomes. As an example, an Outcome can be "Success" but the Validate State may be "Invalid".