The Collaborative International Dictionary of English v.0.48:

Endoscope \En"do*scope\, n. [Endo- + -scope.] (Med.)
   An instrument for examining the interior of the body,
   consisting of a flexible tube with lenses and optical fibers
   permitting illumination of the interior site to be inspected,
   and visualization of the interior site from outside the body;
   it often has small surgical instruments attached to the end
   and manipulable from the outside, permitting biopsy or
   surgery. It is used as a non-invasive or minimally invasive
   tool for diagnosis or treatment, especially in organs having
   an external opening such as the rectum, the urethra, and the
   bladder.
   [1913 Webster +PJC]

WordNet (r) 3.0 (2006):

endoscope
    n 1: a long slender medical instrument for examining the
         interior of a bodily organ or performing minor surgery