Absinthe.
Absinthe is composed of the tops and leaves of the herb artemisia absinthium, or wormwood, which contains a volatile oil, absinthol, and a yellow, crystalline, resinous compound, called absinthin, which is the bitter principle. The alcohol with which this is mixed holds these volatile oils in solution.
The free use of absinthe is injurious. Never serve it in any kind of drink unless called for by the customer.