Chewing loudly with your mouth open. Usual offenders are people chewing gum, or those that have blocked sinuses who are unable to chew with their mouths closed. Name comes from the 'chanka-chanka-chanka' sound of someone doing this.
Just my luck to be stuck on a train full of people chanking loudly on their food.
"Charlie was cranky all day on account of a vigorous all night chanking session."
"Kill Bill fans were tonight shocked to hear of the horrific chanking death of David Carridine. Initial autopsy reports indicate that the movie star may have literally chanked his brains out."
"It's all TV dinners for me these days since the Mrs has discovered chanking!"