telescoping
movement of one part sliding out from another, lengthening an object, or quality of a mechanism that performs such a movement
en-US/ˈtɛlɪˌskoʊpɪŋ/
en-GB/ˈtɛlɪskəʊpɪŋ/
movement of one part sliding out from another, lengthening an object, or quality of a mechanism that performs such a movement