First meal is a traditional feast celebrated on the planet Meridian when it returns to normal space after a sixty year period in a separate dimension.
While in the separate dimension, the planet and its inhabitants exist in a non-corporeal form. Thus, the return to physcial form and all its sensations is an event that is much anticipated. First meal is a celebration of this existence and, as the first opportunity to eat in over 60 years, is 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")