First meal was a traditional feast celebrated on the planet Meridian when it returned to normal space after a sixty-year period in a separate dimension. Its counterpart was known as last meal.
While in this separate dimension, the planet and its inhabitants existed in a non-corporeal state. Thus, the return to corporeal form and all its sensations was an event that was much anticipated. First meal was a celebration of this existence and, as the first opportunity to eat in over sixty years, was lavish and filled with good will.
In 2371, Benjamin Sisko, Jadzia Dax, Julian Bashir, and Miles O'Brien were guests at first meal. (DS9: "Meridian")