To observe a day (or event) with ceremonies of respect, festivity, or rejoicing.
To perform a religious ceremony: celebrate Mass.
To extol or praise: a sonnet that celebrates love.
To make widely known, to display outwardly.
"Earth, water, air, and fire, with feeling glee, Exult to celebrate thy festival" -- Thomson.
To commemorate, distinguish, honour.
Usage: We commemorate events which we desire to keep in remembrance, when we recall them by some special observance. We celebrate by demonstrations of our joy or solemnity or by appropriate ceremonies.
Commemorate: bless, carouse, ceremonialize, dedicate, exalt, extol, glorify, honour, memorialize, proclaim, revere, solemnize.
Exult: be joyful, be delighted, be elated, be happy, be jubilant, be overjoyed, cheer, jubilate, make merry, rejoice.