1. Adj.Final: our ultimate goal/aim/objective/target. We will accept ultimate responsibilities for whatever happens. This is my ultimate decision. The ultimate decision lies on the boss.
2. Most extreme: best, worst, longest, hardest, the most important, etc. The exam will be the ultimate test to your skills. That was the ultimate day in her life. The experiment brought out the ultimate result.
3. Fundamental. The ultimate principles of our life
4. Noun. The... in sth. The best, most advanced, biggest, greatest and etc. of its kind. Ye is the ultimate in our class. He is the ultimate in architecture