GEOTHERMAL Meaning of GEOTHERMAL in English ge ‧ o ‧ ther ‧ mal /ˌdʒiːəʊˈθɜːm ə l◂ $ -oʊˈθɜːr-/ BrE AmE adjective relating to or coming from the heat inside the Earth:a geothermal energy plant Longman Dictionary of Contemporary English. Longman - Словарь современного английского языка. 2012