n any of five related nonmetallic elements (fluorine or chlorine or bromine or iodine or astatine) that are all monovalent and readily form negative ions
n a coarse annual herb introduced into North America from Siberia; dangerous to sheep and cattle on western rangelands because of its high oxalate content
n a coarse annual herb introduced into North America from Siberia; dangerous to sheep and cattle on western rangelands because of its high oxalate content