Colloquial Scottish term referring to a certain type of young person, characterised by tendency towards wearing Kappa shellsuits, listening to bad techno music, drinking cheap booze (such as the infamous Buckfast "tonic wine"), and indulging in casual drunken violence on a Friday night.
Neds always like football, and neds from Glasgow invariably support either Celtic or Rangers, and will happily fight anyone who supports the other.
For Americans - neds likely derive from the same genetic stock as the redneck, or white trash.