Someone who pushes past official limits in terms of expression and demeanor, serving to test the boundaries between what could nominally get one fired and what WILL get one fired. From the use of songbirds in mining, whose greater susceptibility to impure air causes them to expire first, serving as a warning to humans.

v. collectively or individually finding someone/something to blame for a problem, as opposed to brainstorming which connotes finding solutions to a problem

n. the act of finding someone/something to blame for a problem

(from a TV ad for HD television)