A word that means "all-powerful," this is usually applied to God.
There is some dispute about what "all" means. There is the old conundrum, "Can God make a rock so heavy He can't lift it?" If He can do everything, then He should be able to create such a rock. But He should also be able to lift it, which is a contradiction in terms.
This highlights the fact that the very concept of being all-powerful is contradictory. Often theists try to get around this by stating that God can only do what is logically possible. However, there are other questions that do not deal with logic. Can God act in a way that is evil? By definition, God is supposed to be omnibenevolent, so the answer is no. Yet people can do many things that are evil, so clearly being evil is logically possible, but God cannot do it.
Then we get to arguments about how being good is "God's nature," and He can only do things that aren't against His own nature. At this point, the concept of omnipotence starts to get completely fuzzy.