1. 最も低い構成材の枠組みまたは支える構造を形成する継続的水平木材で成る構造的部材(structural member consisting of a continuous horizontal timber forming the lowest member of a framework or supporting structure)
2. (地質学)2つの古い堆積岩の層の間の、平坦な(通常水平な)火成岩体(a flat (usually horizontal) mass of igneous rock between two layers of older sedimentary rock)