The phrase "common definition" refers to a definition that most people agree on or use to describe something. It means that a large group of people share the same understanding or idea of what something means. Full definition
-- the most common definition of what is happening in the cryptocurrency market. (links2exchange.net)
For now, just understand that the most common definition of co sleeping is simply sleeping with your baby closer to you than in a crib in a separate room. (abckidsinc.com)