Meaning

noun (zoology) cessation or slowing of activity during the summer; especially slowing of metabolism in some animals during a hot or dry period

noun (botany) the arrangement of sepals and petals in a flower bud before it opens

originBorrowed from Latin aestīvātiō, from Latin aestīvō, aestīvāre (“to spend or pass the summer in a place”), from aestīvus (“of or pertaining to summer”), from aestās (“summer”) + -īvus.

Etymology from Wiktionary, CC BY-SA 3.0