The term 'MANY A GUINNESS BOOK RECORD' can be summarized as a phrase that refers to the many records that have been documented in the Guinness Book of World Records. The crossword solution for this term is 'FEAT', which is an abbreviation for 'featuring' or 'FEAT'. This term is used to describe an accomplishment or remarkable achievement, which is what the Guinness Book of World Records is all about.