thor|ough|wort «THUR oh WURT», noun.
1. a North American composite herb that has opposite leaves, each pair united at the base so that the stem appears to grow through them, and large corymbs of numerous white flowers; boneset; agueweed; trumpetweed. It is valued for its tonic and diaphoretic properties.
2. any one of several other plants of the same group.
Useful english dictionary. 2012.