The Collaborative International Dictionary of English v.0.48:

Gautama \Gau"ta*ma\ (gou"t[.a]*m[.a]), prop. n.
   The family name of Buddha, the founder of Buddhism; born
   ca. 563 b.c., died ca. 483 b.c. In He is worshipped by
   Buddhists as a god. See Buddha. [Also spelled Gotama.]

   Syn: Buddha, the Buddha, Siddhartha, Gotama, Gautama Buddha.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

Gautama
    n 1: founder of Buddhism; worshipped as a god (c 563-483 BC)
         [syn: Buddha, Siddhartha, Gautama, Gautama
         Siddhartha, Gautama Buddha]