I like that the verbs to telescope and to concertina are synonyms and antonyms of each other. At least, they are in my vocabulary.
To concertina means “to extend, contract, or compress in the manner of a concertina organ.” Every dictionary I checked says to telescope means “to contract, slide, or collapse (into itself) in the manner of a telescope.”
However, to me to telescope also means to “extend or project (out of itself) in the manner of a telescope.” I see that I am not alone, although the most common form by far is telescope out. I suspect this peculiarity of my idiolect is from a lifetime of fooling with portable radios, where a “telescoping antenna” was an asset, the longer, the better.