From Longman Dictionary of Contemporary Englishcritical massˌcritical ˈmass noun [countable, uncountable] 1 HPthe amount of a substance that is necessary for a nuclear chain reaction to start2 the smallest number of people or things that are needed in order for something to happen or be possible How can we get a critical mass of people involved to keep the club running?
Examples from the Corpus
critical mass• Movie crowds create commercial critical mass, especially after hours.• Some thing or things have to happen for a microbe to escape its previously harmless ecological niche and reach critical mass.• The clusters helped recruit businesses, created the critical mass needed to start programs, and provided work-based learning opportunities for students.• He used his position power to effect the critical mass that was necessary to make the change.• By using critical mass and monolithic buying power, we can change the way we do business.From Longman Business Dictionarycritical massˌcritical ˈmass noun [singular]COMMERCEMARKETING the minimum number of users, buyers etc that is necessary for a product to succeed or for something to happencritical mass ofA communications system is of no value to the users unless there is a critical mass of users. 