/ ˈmegəlɪθ; NAmE / noun
a very large stone, especially one put in a place that was used for ceremonies in ancient times
► mega·lith·ic / ˌmegəˈlɪθɪk; NAmE / adjective
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WORD ORIGIN
mid 19th cent.: back-formation from megalithic , from mega- large + Greek lithos stone.