A person who has no particular skill or specialist knowledge, but who is regarded as capable of doing reasonably well across a range of responsibilities; and whose principal value to a business is an ability to absorb new information quickly. Often working in financial services, a spongible person will never set the market alight, but is ideal for fighting fires.
Banker 1: Tyson has lost the bank millions, we need to appoint someone who can quickly grasp the issues but won't be missed in his current job and won't go after mine.