Noun

1. 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
2. Someone able to acquire new knowledge and skills rapidly and easily
3. A follower who hangs around a host (without benefit to the host) in hope of gain or advantage
4. Primitive multicellular marine animal whose porous body is supported by a fibrous skeletal framework; usually occurs in sessile colonies

Verb

1. Wipe with a sponge, so as to clean or moisten
2. Ask for and get free; be a parasite
3. Erase with a sponge; as of words on a blackboard
4. Soak up with a sponge
5. Gather sponges, in the ocean