trephine

n (medical 医) surgeon's cylindrical saw used for this （做以上手术用的）环钻, 环锯.

tremella, tremendous, tremendously, tremolo, tremor, tremulous, tremulously, trench, trench coat, trenchant, trenchantly, trencher, trencherman, trend, trend-setter, trend-setting, trendily, trendiness, trendy, trepan, trepidation, trespass, trespasser, tress, trestle, trestle-table, trews, tri-, triad, trial, trial run, triangle, triangular, tribal, tribalism, tribe, tribesman, tribulation, tribunal, tributary,