used to say that you hope someone will have a happy time at Christmas [= Happy Christmas]
happy [= cheerful, jolly]:
He marched off, whistling a merry tune.
He's a lovely man with merry eyes and a wide smile.
used to say that you are happy for other people to join you in what you are doing:
'Do you mind if I bring Tony?' 'No, of course not. The more the merrier.'
4 [not before noun] British English informal
slightly drunk [= tipsy]
to enjoy yourself by drinking, singing, laughing, etc:
Christmas is a time to eat, drink and make merry.
6 old use
the merry month of June