1. A vote variation used for elections in which each voter may “approve” of (that is, select) any number of candidates. Typically, the winner is the most-approved candidate.
Source: Election Terminology Glossary - Draft, National Institute of Standards and Technology (NIST), https://pages.nist.gov/ElectionGlossary/
2. A voting method in which a voter may vote for an arbitrary number of candidates (the ones of which she [he] “approves”), the candidate receiving the highest number of votes being the winner.
Source: Electronic Voting Glossary, Michael I. Shamos, https://collaborate.nist.gov/voting/pub/Voting/Glossary/Shamos-Election-Glossary.pdf