I do not know if there is such a term but there isw a term reducer. For example I do have a Celestron 0.63 reducer.The reverse is also true: A 0.5x TC gains 2 stops.
Those are usually sold as speed boosters to use a full frame lens on a crop camera. If i recall correctly, some lens designs with a wide angle and a large aperture have such an element built in.
In astronomy terms, I think these gadgets are called "telecompressors". I used one on my Celestron 8-inch to reduce the EFL from 2000/11 to 1000/5.6, or something like that.