Intussusception is a condition in which the bowel __________ into itself.

In the case of intussusception, the bowel indeed telescopes into itself. This phenomenon occurs when a portion of the intestine slips or telescopes into an adjoining segment, leading to a blockage. This condition can disrupt blood flow and lead to serious complications if not treated promptly.

The other options do not accurately describe the mechanism of intussusception. For example, inflation refers to the process of becoming swollen due to an increase in air or fluid, rather than a specific action of one part of the bowel entering another. Reversal suggests an opposite directional motion that does not apply to this condition, and swelling indicates an enlargement or inflammation rather than the distinct action of one part of the bowel sliding into another. Consequently, "telescopes" is the term that most precisely defines this medical condition.