Dictionary.net

An judge’s admonition to a deadlocked jury to go back to the jury room and try harder to reach a verdict. The judge might remind the jurors to respectfully consider the opinions of others and will often assure them that if the case has to be tried again, another jury won’t necessarily do a better job than they’re doing. Because of its coercive nature, some states prohibit the use of a dynamite charge as a violation of their state constitution, but the practice passed Federal constitutional muster in the case of Allen v. Gainer. The instruction is also known as a dynamite instruction, shotgun instruction, Allen charge or third degree instruction.