Definition of "knuckle" []

• The prominence of the dorsal aspect of a joint of a finger, especially of one of the joints connecting the fingers to the hand. (noun)
• A rounded protuberance formed by the bones in a joint. (noun)
• A cut of meat centering on the carpal or tarsal joint, as of a pig. (noun)
• The part of a hinge through which the pin passes. (noun)
• A sharp angle formed by the meeting of two surfaces, especially two ship's timbers. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "Our "humble pie" is their "humble sandwich": people do actually use the expression "knuckle sandwich" to describe a punch here, and Obama's deal to raise the debt ceiling was unanimously panned as "a sugar-coated Satan sandwich"."
• "Though it was well after midnight, everyone was hustled onto a bus for what she describes as a knuckle-biting three-hour trip to their scheduled destination."
• "Of course they did not use what we call knuckle-dusters, nor did they even double their fists, except when moving round each other, and as "gloves" were unknown, they struck out with the hands half open, for they had no wish to bleed each other's noses or black each other's eyes for mere amusement."