PTSot 17.b:16[2] :כורתא דחרוביתא‏ : the trunk of the carob tree
See the entire entry for ḥrwby n.f. carob tree

PTSot 17.b:16[2] :מקפא {בירתא}<כורתא> דחרובתיה דארעא דיש׳‏ : to (measure) around the trunks of the Land of Israel's carob trees
See the entire entry for kwrt n.m. tree trunk

PTSot 17.b:16[2] :מקפא כורתא דחרוביתא‏ : in order to encircle (with the belts) the trunk of the carob tree
See the entire entry for nqp vb. to circle around, surround