As Ben D will happily agree, there are many things we both strenuously disagree on, however on his description above he is largely quite correct.
In even simpler terms, which
@ben d may or may not agree with.... In meditation, one transcends the subject/object divide whereas in prayer, by its very nature, one maintains or strengthens the subject/object divide (in all but the rarest of cases). Would you agree, Ben D?
The net result is that they are very different practices. Likewise, meditation is Abrahamic religions is a very different beast from the meditation practices in Eastern traditions. Meditation, in Abrahamic terms is more akin to contemplation.