• (n.) A name given to several resinous-glandular composite plants of California, esp. to the species of Grindelia, Hemizonia, and Madia. Found on http://thinkexist.com/dictionary/meaning/tarweed/
any sticky, hairy plant of the genus Madia of the family Asteraceae, consisting of about 18 species. They are native to western North and South ... Found on http://www.britannica.com/eb/a-z/t/14
Tar'weed` noun (Botany) A name given to several resinous-glandular composite plants of California, esp. to the species of Grindelia , Hemizonia , and Madia . Found on http://www.encyclo.co.uk/webster/T/14