The term AD-LIB (WING IT) is a phrase that means to improvise or make up something on the spot. It is derived from the Latin phrase 'AD libitum, ' which translates to 'at one's pleasure.' The crossword solution for this term is LIB, which is an abbreviation of the word 'LIBRARY.' This is because libraries are often associated with improvisation and creativity, as they are filled with books that can provide inspiration and ideas.