According to Chamber's 21st Century Dictionary,
verb (intervened, intervening) intransitive
1. (often intervene in something) to involve oneself in something which is happening in order to affect the outcome.
2. (often intervene in something or between people) to involve oneself or interfere in a dispute between other people in order to settle it or prevent more serious conflict.
3. to come or occur between two things in place or time."
God's intervention is an important aspect of many theist's beliefs. It is one of those areas that has always confused me to some degree. I have never understood how so many can fail to see the innate contradiction and irrational nature of this view. Many of those who believe firmly that God intervenes on their behalf also insist that God is the creator and source of all things. By definition this would imply that God either does not intervene or is not the source of all things. How do you intervene if you are the source of the effect or interaction in question? Reread the above definition. Does it not indicate a third, previously uninvolved, party?
It is actually possible to interfere with your own plan or action once it is set in motion but that is not generally what we mean when we use the term "intervene." This also poses a number of other theological problems. If God is the source and then "intervenes" wouldn't this indicate a mistake? Most theists would also agree that God is perfect. If God finds it necessary to interfere with what has been set in motion that would seem to imply that God is imperfect. If you accept perfection as a defining trait of God then intervention becomes a contradictory and untenable view. Rather, it would, if you apply anything resembling critical thinking.