Terrabioforming is a compromise process that is partly terraforming (making a world habitable) and partly bioforming (changing ourselves to live in exotic environment). It is a sort of meet halfway process. While there are complex multicellular animals that are extremophiles, e.g. anaerobic loriciferans and hyperthermophilic (over 80 degrees Celsius) Pompeji worms, there is also the fact that intelligent brains consume much energy. For example, food scarcity would make most of the deep sea uninhabitable to intelligent genetically engineered (post)humans adapted to high pressure, total darkness and underwater breathing (though some would be able to live near the richest hydrothermal vents).
A terrabioforming process would most likely be one of increasing the productivity of an environment that already supports extremophilic life, from one where no intelligent life can find enough food to one where genetically engineered extremophile human strains can survive (though still lethal to unmodified humans). Combined with suitable genetic engineering of some humans.
The low gravity, high heavy metal content in the soil, and requirement of greater greenhouse concentration for increasing temperature makes full classical terraforming of Mars unlikely, while terrabioforming is much more likely. Terrabioforming will, by allowing modified humans to survive at high CO2 levels, high radiation levels and low O2 (oxygen) levels lethal to unmodified humans, be much faster than classic terraforming. Mere decades.