borescope

noun

1. An optical instrument used for seeing inside tight spaces, consisting of a rigid or flexible tube with an optical relay inside so that the view through a lens or window at one end of the tube may be seen from a lens or eyepiece in the opposite end of the tube.

verb

1. To see inside or examine (something) using a borescope.

   “Maintenance borescoped the jet engine to check for damaged turbine blades.”