The word "reboard" can be defined as getting on board again or boarding again. There are a few synonyms for this word including rejoin, re-enter, and re-mount. Rejoin refers to returning to a group or organization that one has left or been separated from. Re-enter refers to going back into a place or situation that one has previously left. Re-mount refers to getting back onto a horse or vehicle that one has come off from. All of these synonyms capture the idea of going back to a previous place or situation, which is what reboard means.