1. Voting that can occur unsupervised at a location chosen by the voter either before or on Election Day.
Source: Election Terminology Glossary - Draft, National Institute of Standards and Technology (NIST), https://pages.nist.gov/ElectionGlossary/
2. The process of voting at other than at a polling place, usually by filling out a ballot and mailing or delivering it to an election authority.
Source: Electronic Voting Glossary, Michael I. Shamos, https://collaborate.nist.gov/voting/pub/Voting/Glossary/Shamos-Election-Glossary.pdf
3. Voting other than in-person at a voter’s assigned voting place; includes vote by mail.
Source: Independent Panel on Internet Voting, British Columbia, https://elections.bc.ca/docs/recommendations-report.pdf