1. To collapse by sliding down and fitting into a larger outer part or section. The lens telescopes into the body of the camera.
2. To cause something to collapse into something in such a manner. In this usage, a noun or pronoun is used between "telescope" and "into." Make sure you telescope the antenna into the base before you pack the radio, or you could end up damaging it.
3. To change into a certain shape by collapsing in such a manner. The drinking cup telescopes into a small disc that you can easily slip into your pocket.
4. To condense something into a shorter, smaller, or more compact form or scale. In this usage, a noun or pronoun can be used between "telescope" and "into." It's going to be tricky to telescope such a sprawling novel into a two-hour movie. It's a shame that thousands of years of human history have to get telescoped into a single lecture, but there's just no way to cover every single event in one semester otherwise.
telescope into something
[for one cylindrical part of something] to fit down inside another part, thereby reducing the length of the whole. This part telescopes into this part. The tent poles telescoped into a small, compact unit.