Cell organelles that contain their own DNA and replicate independently of the nucleus are said to be semi-autonomous.
Mitochondria have their own DNA which is capable of replicating independently.
Mitochondria are also partly independent or semi-autonomous as they can manufacture some of the proteins required for their effective functioning with help of their DNA, RNAs, enzymes, and ribosomes & obtain others from the cytoplasm formed under the control of the nuclear DNA.
The organelles also possess their own ribosomes, called mitoribosomes.