What is "absinthium"

Absinthium \Ab*sin"thi*um\, n. [L., from Gr. ?.] (Bot.) The common wormwood ( Artemisia absinthium), an intensely bitter plant, used as a tonic and for making the oil of wormwood.

n. 1 (context now rare English) The common wormwood (''Artemisia absinthium''), an intensely bitter herb used in the production of absinthe and vermouth, and as a tonic. (First attested around 1150 to 1350.)(reference-book editor=Brown, Lesley title=The Shorter Oxford English Dictionary origyear= 1933 edition = 5th year=2003 publisher=Oxford University Press location=Oxford, UK isbn =978-0-19-860575-7 pages =9 ) 2 The dried leaves and flowering tops of the wormwood plant; absinthe oil.(R:MW3 1976: page=5)