Bull Rush

When a creature wants to push another creature away, the bull rush power is a good option. Although many classes and monsters have powers that can push a target farther, the advantage of bull rush is that anyone can use it, regardless of class.
    The bull rush power is useful for forcing an enemy out of a defensive position or into a dangerous one, such as into a pool of lava or over a cliff. It can also do useful things such as pushing an ally out of an enemy’s grasp.

BULL RUSH: STANDARD ACTION

Target: You can bull rush a target adjacent to you that is smaller than you, the same size category as you, or one category larger than you.

Strength Attack: Make a Strength attack vs. Fortitude defense. Do not add any modifiers for the weapon you use.
Hit: Push the target 1 square, and shift into the vacated space.

Impossible Push: If there’s no square you can push the target into, your bull rush has no effect.

Published in Player's Handbook, page(s) 287, Rules Compendium, page(s) 239.