To become dense or more dense.
To collapse, via cancellation.
To extend or contract in the manner of a telescope.
To slide or pass one within another, after the manner of the sections of a small telescope or spyglass.
To come into collision, as railway cars, in such a manner that one runs into another.
Any instrument used in astronomy for observing distant objects (such as a radio telescope).
A monocular optical instrument that magnifies distant objects, especially in astronomy.
A retractable tubular support for lights.