[rad.i.cal] adj [ME, fr. LL radicalis, fr. L radic-, radix root--more at root] (14c) 1: of, relating to, or proceeding from a root: as a (1): of or growing from the root of a plant "~ tubers" (2): growing from the base of a stem, from a rootlike stem, or from a stem that does not rise above the ground "~ leaves" b: of, relating to, or constituting a linguistic root c: of or relating to a mathematical root d: designed to remove the root of a disease or all diseased tissue "~ surgery"
2: of or relating to the origin: fundamental 3 a: marked by a considerable departure from the usual or traditional: extreme b: tending or disposed to make extreme changes in existing views, habits, conditions, or institutions c: of, relating to, or constituting a political group associated with views, practices, and policies of extreme change d: advocating extreme measures to retain or restore a political state of affairs "the ~ right"
4. slang: excellent, cool -- rad.i.cal.ness n
[2]radical n (1641) 1 a: a root part b: a basic principle: foundation
2. a: root
6. b: a sound or letter belonging to a radical
3: one who is radical
4: free radical; also: a group of atoms bonded together that is considered an entity in various kinds of reactions
5. a: a mathematical expression indicating a root by means of a radical sign b: radical sign