tropospherePronunciation: /ˈtrɒpə(ʊ)sfɪə, ˈtrəʊp-/Definition of troposphere noun the lowest region of the atmosphere, extending from the earth’s surface to a height of about 6-10 km (the lower boundary of the stratosphere). Derivatives troposphericPronunciation: /-ˈsfɛrɪk/ adjective Origin: early 20th century: from Greek tropos 'turning' + spheretroposphere in other Oxford dictionaries Definition of troposphere in the US English dictionary