Power Bash is one of the nine perks of Block in The Elder Scrolls V: Skyrim. It can be used with any shield or blocking weapon, but consumes more stamina than a normal bash. It can be improved by a following perk to increase its damage by 5 times. To execute a Power Bash, simply hold the action button instead of clicking it once, just like performing a Power Attack with any melee weapon. The Power Bash staggers enemies for a noticeably longer period of time than the regular bash does, in addition to doing more damage.
It has the side effect of draining the Dragonborn's stamina whether they hold the action button or tap it.