1. Vote that could not be allocated to a specific contest due to an undervote or overvote.
Source: Election Terminology Glossary - Draft, National Institute of Standards and Technology (NIST), https://pages.nist.gov/ElectionGlossary/
2. Total number of votes that cannot be counted for a specific contest. There may be multiple reasons for residual votes (e.g., declining to vote for the contest, over-voting in a contest).
Source: Glossary of terms database, U.S. Election Assistance Commission, https://www.eac.gov/glossary/
3. The sum of overvotes and undervotes for a given election contest.
Source: Asking the Right Questions about Electronic Voting, National Research Council on the National Academies, https://www.nap.edu/catalog/11449/asking-the-right-questions-about-electronic-voting