Source : Webster's Revised Unabridged Dictionary (1913)

Alecost \Ale"cost`\, n. [Ale + L. costus an aromatic plant: cf.
   {Costmary}.] (Bot.)
   The plant costmary, which was formerly much used for
   flavoring ale.

Source : WordNet®

alecost
     n : tansy-scented Eurasian perennial herb with buttonlike yellow
         flowers; used as potherb or salad green and sometimes for
         potpourri or tea or flavoring; sometimes placed in genus
         Chrysanthemum [syn: {costmary}, {bible leaf}, {mint
         geranium}, {balsam herb}, {Tanacetum balsamita}, {Chrysanthemum
         balsamita}]