Estivation (or aestivation, if you're in Europe) is the summertime version of hibernation, when animals go into a state of dormancy to lessen the effects of high temperatures and/or drought. While an estivating animal's bodily rhythms do slow, they are not as fully dormant as animals who hibernate in the winter. That means they are able to more quickly awaken and respond to situations (or changes in their environment).
Animals who estivate include the fat-tailed lemur (the first mammal discovered who estivates); many reptiles and amphibians, including the North American desert tortoise, the spotted turtle, the California tiger salamader, and the water-holding frog; certain air-breathing land snails; and some insects, including bees, earthworms, and lady bugs.
California Tiger Salamander (Ambystoma californiense) by John Cleckler [Public domain], via Wikimedia Commons
Ladybug (Coccinella magnifica) by Gilles San Martin [CC BY-SA 2.0], via Wikimedia Commons
Spotted Turtle (Clemmys guttata) by John J. Mosesso, NBII [Public domain], via Wikimedia Commons