When your palm itches it usually signifies that you will be receiving money in the near future.
Left=Loss of Money
When your right palm itches, do not scratch your hand for the "luck" will go away. But if your left itches, then scratch away to ward off the loss.
It also means you'll get laid by the ugliest chick and regret it the next day
"Man I had an itchy palm and I found 20 bucks later that day!"
"Man I had an itchy palm last night"
The condition of being so intensely irritated by someone that you want to slap them, and thus relieve the itchiness of your palms.
Paris Hilton is giving me itchy palms. I'll have to slap her.