The region of discontinuity between the troposphere and the stratosphere WordNet 3.0 & Open English WordNet

The tropopause is the atmospheric boundary that demarcates the troposphere from the stratosphere, which are the lowest two of the five layers of the atmosphere of Earth. Wikipedia

Upper boundary of troposphere Wikidata

The zone of transition between the troposphere and the stratosphere. OmegaWiki

The zone of transition between the troposphere and the stratosphere (approximately 13 kilometers). The tropopause normally occurs at an altitude of between 25,000 and 45,000 feet in polar and temperate zones. It occurs at 55,000 feet in the tropics. Wiktionary

Zone of transition between troposphere and stratosphere. Wiktionary (translation)