From WordNet (r) 3.0 (2006) [wn]:
Vishnu
n 1: the sustainer; a Hindu divinity worshipped as the preserver
of worlds
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Vishnu \Vish"nu\ (v[i^]sh"n[=oo]), n. [Skr. Vish[.n]u, from vish
to pervade., to extend through nature.] (Hindu Myth.)
A divinity of the modern Hindu trimurti, or trinity. He is
regarded as the preserver, while Brahma is the creator, and
Siva the destroyer of the creation.
[1913 Webster]