Nickname for the secondary of the 2013 Super Bowl Champion Seattle Seahawks. The Legion of Boom original members were Earl Thomas III, Richard Sherman, Kam Chancellor and Brandon Browner. Newest additions are Walter Thurmond III, Jeremy Lane and Byron Maxwell. Due to the nature of how hard hitting and fast the Seahawks defense is the whole D is starting to take on The Legion of Boom moniker with the national media.
The Seahawks Legion of Boom put a hurting on the Denver Broncos and Peyton Manning in Super Bowl XLVIII to the tune of 43-8.
'Grah Grah Boom' is a sound made by only the hardest drill rappers and crazies on the streets.
It is an onomatopoeia for loud, hard hitting gunshots, particularly from a large caliber firearm that can decapitate the average gangbanger with a single bullet. It is frequently used as an adlib in various rap videos.
It can also be used to threaten someone, especially other rival gang members (Mostly in the Bronx or Chicago) with a gun, or to diss dead gang members.