Wicked means really, extremely, or very. Moslty used in New England around Boston and what not. If you use wicked and aren't near Boston or somethinh people are going to think your stupid because they won't know what it means. Believe me I would know, consider it advice from one New Englander to another
A word that originally came from the English underground. Used in the same way as a person from the Northeast United States to give more expression than the words very or cool.