gir·dle (gûrʹdl)brilliant-cut gemstonePrecision Graphicsn. 1. a. A belt or sash worn around the waist. b. Something that encircles like a belt. c. An elasticized, flexible undergarment worn over the waist and hips, especially by women, to give the body a more slender appearance. 2. A band made around the trunk of a tree by the removal of a strip of bark. 3. The edge of a cut gem held by the setting. 4.Anatomy. The pelvic or pectoral girdle.tr.v. gir·dled, gir·dling, gir·dles 1. To encircle with or as if with a belt. See Synonyms at surround. 2. To circle around: a ring of hills that girdled the city. 3. To remove a band of bark and cambium from the circumference of (a tree), usually in order to kill it. [Middle English girdel, from Old English gyrdel. See gher-1 in Indo-European Roots.]