a) someone's singing that sounds so horrendously bad it's as if a hen or rooster is literally scratching a blackboard.
b) a synonym, used mainly in Alberta in Western Canada, for turkey-chicken scrawl or terrible penmanship
person a): hang on, what's this hen-scratching?
person b) i think it's my friend Paul trying to sing, but he's singing out of tune with our high school band..
person a) roflmao