[only before noun] used to describe the highest level of something, or a time when the greatest number of people are doing something or using something It was a time of peak demand for the product. March is one of the peak periods for our business. The athletes are all in peak condition. We need extra help during the peak season. compare off-peak See related entries: Trends Word Origin mid 16th cent.: probably a back-formation from peaked, variant of dialect picked ‘pointed’.