Bloodrush

Bloodrush is an ability word introduced in Gatecrash, wherein it is the Gruul Clans guild mechanic. It allows players players to discard creature cards in order to give an attacking creature a temporary power/toughness boost equal to the power and toughness of the discarded creature card.

Rulings

The bonus for each bloodrush ability is tied to the power, toughness, and other abilities of the creature card with bloodrush.

Example

Rubblehulk -
Creature — Elemental
*/*
Rubblehulk's power and toughness are each equal to the number of lands you control.
Bloodrush — , Discard Rubblehulk: Target attacking creature gets +X/+X until end of turn, where X is the number of lands you control.