ST segment
noun
variants:
or S-T segment \ ˌes-ˈtē- 
\
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Medical Definition of ST segment
: the part of an electrocardiogram between the QRS complex and the T wave
… he had no chest pain, lacked a high coronary risk profile, and had normal ST segments on maximal effort.— John Davis Cantwell, Physician and Sportsmedicine, March 1981