'Water bed' definitions:

Definition of 'water bed'

From: WordNet
noun
A bed with a mattress made of strong plastic that is filled with water

Definition of 'Water bed'

From: GCIDE
  • Water bed \Wa"ter bed`\ A kind of mattress made of, or covered with, waterproof fabric and filled with water, thus providing uniform support to the body lying on it; -- also a bed constructed so as to contain such a mattress. It is used in hospitals for bedridden patients, as well as in some private homes. [1913 Webster +PJC]