Thermostable

 Thermostable means to not be affected or changed by heat or high temperatures. With regard to biology and science, a thermostable enzyme is one that can withstand high temperatures without being denatured and rendered inactive. 

For example, during PCR, a thermostable enzyme (usually Taq polymerase) is used to withstand the high temperatures needed to denature DNA. DNA polymerase was the enzyme used before, however it needed to be added each cycle as it would be dentatured during the proceedure.