Merriam-Webster Collegiate Dictionary - circumvallate

 I. transitive verb  (-lated; -lating)  Etymology: Latin circumvallatus, past participle of circumvallare to surround with siege works, from circum- + vallum rampart — more at wall  Date: circa 1798 to surround by or as if by a rampart  • circumvallation noun  II. adjective  Date: circa 1852 being any of approximately 12 large papillae near the back of the tongue each of which is surrounded with a marginal sulcus and supplied with taste buds responsive especially to bitter flavors