The Collaborative International Dictionary of English v.0.48:

Leninism \Leninism\ prop. n.
   a form of communism based on the writings of Marx and Lenin;
   called also Marxism-Leninism.

   Syn: bolshevism, collectivism, Marxism-Leninism, Marxism,
        Sovietism, sovietism.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

Leninism
    n 1: the political and economic theories of Lenin which provided
         the guiding doctrine of the Soviet Union; the modification
         of Marxism by Lenin stressed that imperialism is the
         highest form of capitalism (which shifts the struggle from
         developed to underdeveloped countries) [syn: Leninism,
         Marxism-Leninism]