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
"The diver carefully extracted the fragile sponge from its rocky crevice, noting how its porous structure allowed it to trap vast amounts of ocean water."
someone able to acquire new knowledge and skills rapidly and easily
"she soaks up foreign languages like a sponge"
Any of various marine invertebrates, mostly of the phylum Porifera, that have a porous skeleton often of silica.
"The diver gently brushed off the colorful sponge growing on the rocky ocean floor before collecting it for his aquarium."
In plain English: A sponge is a soft, porous material that soaks up liquids and can be squeezed to release them again.
"She used an old sponge to scrub the kitchen sink."
Usage: As a verb meaning to exploit someone's generosity, "sponge" is informal and typically requires an object (e.g., "don't sponge off your parents"). Do not confuse this with the noun referring to the porous marine animal or the cleaning tool made from one.
wipe with a sponge, so as to clean or moisten
"After washing the dishes, she used a wet sponge to wipe down the greasy countertop."
erase with a sponge; as of words on a blackboard
"The teacher asked the student to wipe out the incorrect answers from the blackboard using an eraser, not a sponge."
soak up with a sponge
"She quickly wiped the spilled milk from the table by pressing a wet sponge against it to soak up every drop."
gather sponges, in the ocean
"The divers dove deep into the coral reef to gather sponges from the sandy ocean floor."
To take advantage of the kindness of others.
"He was accused of sponging off his wealthy parents instead of finding a job on his own."
In plain English: To sponge is to soak up liquid quickly, just like how a kitchen towel absorbs water from dishes.
"I will sponge off the spilled milk from the kitchen floor before my mom comes home."
The word "sponge" entered English via the French language as a loanword. It originally referred to the marine animal before taking on its modern meaning of an absorbent cleaning tool.