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1.
A person who revels in a festive party.
A merrymaker would be a person as excited and marry as the host at her 20th birthday costume party, which happens to be going wonderfully & every one shows up wearing a costume.

Even without the whole costume part, a marrymaker is someone who indulges in unrestrained, noisy, rowdy, and fun environments.
by bfeather January 06, 2010