n. [ Gr. &unr_; almond + -oid: cf. F. amygdaloïde. ] (Min.) A variety of trap or basaltic rock, containing small cavities, occupied, wholly or in part, by nodules or geodes of different minerals, esp. agates, quartz, calcite, and the zeolites. When the imbedded minerals are detached or removed by decomposition, it is porous, like lava. [ 1913 Webster ]

{ } a. 1. Almond-shaped. [ 1913 Webster ]

2. Pertaining to, or having the nature of, the rock amygdaloid. [ 1913 Webster ]