In most jurisdictions, you can request an absentee ballot, or a "vote by mail" ballot. Some places require a justification for an absentee ballot, but in many places it's available to anyone who asks.

You can vote by absentee ballot. I was living in Germany when I was able to vote for my first presidential election and voted absentee ballot.

When a person votes in an election using a ballot obtained from his county election officer either in person beforehand or by mail what is it called voting by absentee ballot.

An absentee voter is a registered voter who is allowed to vote by absentee ballot, due to absence from the district during the election.