Derived from the Simpsons episode "Post Cards from the Wedge," a prayer block is done when one makes a prayer before another person and, on perpose, negating another persons prayer with one's own prayer.
ex. 1

Marge: (While praying) Dear Lord, please give my stubborn husband the wisdom to see that I am right as usual.
Homer: Too late Marge, I already use the prayer block on your prayer.

ex 2
Guy: Thank god I did a prayer block months ahead so the Yankees could win another World Series.
by PM05orig March 18, 2010
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