What does Merry Meet mean?

It is possible that you've heard Wiccans, Pagans, and Witches say 'Merry Meet' when they greet each other. But what does it mean?

It’s a greeting that comes from the common expression used when closing a circle after a ritual, 'Merry Meet, Merry Part, and Merry Meet Again.' 

This comes from a poem by either Lady Gwen Thompson or (it is suggested) her grandmother, Adriana Porter, called The Rede of the Wiccae. 

One of the lines in the poem is, 'Merry Meet and Merry Part, Bright the Cheeks, and Warm the Heart.' The poem’s last line contains the Wiccan Rede, which is 'An it harm none, do what ye will.'