Noun
teleconverter (plural teleconverters)
English Wikipedia has an article on:teleconverterWikipedia
(photography) A secondary lens mounted between the camera and a photographic lens so as to enlarge the central part of an image obtained by the objective lens.
Also a highly corrected (for macro) 2X teleconverter. Source: Internet
I have 40 year old Pentax A lenses that work very well on my K3 and K5, even with an old 2x teleconverter. Source: Internet
The construction of the teleconverter has been significantly upgraded for both durability and optical brilliance. Source: Internet