estivation n (zoology) cessation or slowing of activity during the summer; especially slowing of metabolism in some animals during a hot or dry period n (botany) the arrangement of sepals and petals in a flower bud before it opens Usage(s) Fortnight ago the 28th had completed three and one-half years of estivation in its mud-pie in a laboratory at New York University Medical College. Synonym(s) aestivation