1. n. [Drilling]

Toolface angle used for deviated wells. Gravity toolface is the angle of the borehole survey instrument within the wellbore measured clockwise relative to up and in the plane perpendicular to the wellbore axis; the high side (maximum build), maximum right, low side (maximum drop) and maximum left directions have gravity toolface angles of 0°, 90°, 180° and 270°, respectively.

Synonyms: high-side toolface

See: magnetic toolface,  toolface