What is the meaning of sponge?

noun

• A porous mass of interlacing fibers that forms the internal skeleton of various marine animals and usable to absorb water or any porous rubber or cellulose product similarly used.
• Someone able to acquire new knowledge and skills rapidly and easily.
  • usage: "she soaks up foreign languages like a sponge"
  • synonyms: quick study
• A follower who hangs around a host (without benefit to the host) in hope of gain or advantage.
  • synonyms: leech, parasite, sponger
• Primitive multicellular marine animal whose porous body is supported by a fibrous skeletal framework; usually occurs in sessile colonies.
  • synonyms: poriferan, parazoan

verb

• Wipe with a sponge, so as to clean or moisten.
• Ask for and get free; be a parasite.
  • synonyms: mooch, bum, cadge, grub
• Erase with a sponge; as of words on a blackboard.
• Soak up with a sponge.
• Gather sponges, in the ocean. .