The Collaborative International Dictionary
Prothalamium
Prothalamion \Pro`tha*la"mi*on\, Prothalamium
\Pro`tha*la"mi*um\, n. [NL., fr. Gr. ? before + ? chamber,
especially, the bridal chamber.]
A song in celebration of a marriage.
--Drayton.
Wiktionary
prothalamium
n. epithalamium