telescope

(transitive, intransitive) To extend or contract in the manner of a telescope.

(transitive, intransitive) To slide or pass one within another, after the manner of the sections of a small telescope or spyglass.

(intransitive) To come into collision, as railway cars, in such a manner that one runs into another.

(transitive, intransitive, mathematics, of a series) To collapse, via cancellation.