1.NounA number whose decimal representation ends in one or more zeroes, especially when it is because the number has only a few significant digits."A well-known anecdote says that the first scientifically precise measurement of Mount Everest's height was purposely misreported to the public as 29,002 feet merely because the actual result, figured at 29,000 feet precisely, sounded like a round number."
2.NounA rough approximation, especially one whose decimal representation ends in one or more zeroes."a nice round number; We don't yet know the exact cost, but 20 million dollars sounds like a nice round number.; In round numbers, the population of the nearest city is about 90,000."