zero population growthn. The lack of an increase in the number of individuals in a given population, occurring when the birth rate equals the death rate.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.ze?ro popula?tion growth` n. a condition in which the population is maintained at a constant level by a balance between the number of births and deaths. [1965?70] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.