noun

1. (historical: 19th-century Britain) A member of the most progressive wing of the Liberal Party; someone favouring social reform (but generally stopping short of socialism).

2. (historical: early 20th-century France) A member of an influential, centrist political party favouring moderate social reform, a republican constitution, and secular politics.

3. A person with radical opinions.

adjective

1. Favoring fundamental change, or change at the root cause of a matter.

   “His beliefs are radical.”

2. Pertaining to a root (of a plant).

3. Pertaining to the basic or intrinsic nature of something.

Synonyms: primitive, fundamental