endoscope

n. instrument for examining the inside of hollow organs (Medicine)

Endoscopy means looking inside and typically refers to looking inside the human body for medical reasons using an instrument called an endoscope. Endoscopy can also refer to using a borescope in technical situations where direct line-of-sight observation is not feasible.
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Endoscope /en·do·scope/ an instrument for examining the interior of a hollow viscus. en·do·scope n. [more]Endoscope - Community and Resources

Noun
1. a long slender medical instrument for examining the interior of a bodily organ or performing minor surgery
(hypernym) medical instrument
(hyponym) arthroscope

(n.)
An instrument for examining the interior of the rectum, the urethra, and the bladder.