Shamrock

sham′rok, n. the national emblem of Ireland, a leaf with three leaflets, or plant having such leaves, sometimes supposed to be the Wood-sorrel, but the name is more frequently applied to some species of Clover, or to some common plant of some of the nearly allied genera, as the Bird's Foot Trefoil or the Black Medick. The Le er Yellow Trefoil is the plant usually sold in Dublin on St Patrick's Day. [Ir. seamrog , Gael. seamrag , trefoil, dim. of seamar , trefoil.]