The '46 defense' is the name of the defensive scheme for the Chicago Bears in the mid/late 80s developed by Buddy Ryan. It was named for the number of safety Doug Plank, whose last year with the Bears was 1982. The idea was the rush the passer with much abandon. Buddy Ryan had this to say about the 46 defense.
“We put it in as a nickel package. We put up eight-man fronts and had run blitzes and pass blitzes."
This scheme was developed to knock players down and out, especially quarterbacks. It helped da Bears win over the New England Patiots in Super Bowl XX along with a run oriented offense plus a good mixture of play action passing.
The defensive scheme was also imortalized in the Public Enemy song, Yo! Bum Rush The Show where Chuck D raps:
While we're hearin' that boom supplement the mix
Gonna rush 'em like the Bears in the 46