NOUN (1)

1. a follower of the economic theories of John Maynard Keynes;


ADJECTIVE (1)

1. of or relating to John Maynard Keynes or to his economic theories;

The Collaborative International Dictionary of English v.0.48:

Keynesian \Keynesian\ adj.
   1. Of or pertaining to John Maynard Keynes; conforming to the
      theories of Keynesianism; -- especially, the term is used
      to refer to the macroeconomic theories and
      politico-economic policies proposed by Keynes and his
      followers, especially in regards to their advocacy of
      governmental action to maintain low unemployment through
      government spending. Keynes's book "The General Theory of
      Employment, Interest, and Money" (Macmillan, 1936) had a
      strong influence on views of the government's role in the
      economy through the 1970's. [WordNet sense 1]
      [WordNet 1.5 +PJC]

   2. A believer in the theories of Keynesianism.
      [PJC]

WordNet (r) 3.0 (2006):

Keynesian
    adj 1: of or relating to John Maynard Keynes or to his economic
           theories
    n 1: a follower of the economic theories of John Maynard Keynes