A hole bored or drilled in the earth as a : an exploratory well, b chiefly British : a small-diameter well drilled especially to obtain water
Merriam – Webster - http://www.merriam-webster.com/dictionary/borehole
The wellbore itself, including the openhole or uncased portion of the well. Borehole may refer to the inside diameter of the wellbore wall, the rock face that bounds the drilled hole.
Schulmberger Oilfield Glossary - http://www.glossary.oilfield.slb.com
Courtesy of https://www.bloemfonteincourant.co.za/boreholes-register-not-register/