SHRUB, among naturalists, denotes a dwarf-tree, or a woody plant less than a tree; such are holly, box, privet, &c. SHUTTLE, in the manufactures, an instrument much used by weavers, in the middle of which is an eye, or cavity, wherein is inclosed the spool with the wool. SI, in music, a seventh note or sound, added by Le Maire to the six ancient notes invented by Guido Aretine, viz. ut, re, mi, fa, sol, la, si.