|Origin:||radicalis, from Latin radix 'root'|
a radical change or difference is very big and important:
They are proposing radical changes to the way the company is run.
a radical reform of the tax system
There are radical differences between the two organizations.
radical ideas are very new and different, and are against what most people think or believe [↪ conservative]:
He has put forward some very radical ideas.
I was shocked by her radical views.
a radical approach to education
someone who is radical has ideas that are very new and different, and against what most people think or believe:
a radical left-wing politician
a radical feminist
very good or enjoyable:
goodAmerican English informal
That was one radical party last night!
a radically different method of production
a radically new approach to the problem