Definition of sponges:
(n) :
(countable) Any of various marine invertebrates of the phylum Porifera, that have a porous skeleton often of silica.
(n) :
(countable) A piece of porous material used for washing (originally made from the invertebrates, now often made of plastic).
(n) :
(uncountable) The porous material that synthetic washing sponges are made of.
(n) :
(informal) A heavy drinker.
(n) :
(countable, uncountable) A type of light cake.
(n) :
(countable, uncountable, British) A type of steamed pudding.