Source : Webster's Revised Unabridged Dictionary (1913)

Loosestrife \Loose"strife`\, n. (Bot.)
   (a) The name of several species of plants of the genus
       {Lysimachia}, having small star-shaped flowers, usually
       of a yellow color.
   (b) Any species of the genus {Lythrum}, having purple, or, in
       some species, crimson flowers. --Gray.

Source : WordNet®

loosestrife
     n 1: any of numerous herbs and subshrubs of the genus Lythrum
     2: any of various herbs and subshrubs of the genus Lysimachia