A Skiddo is a Script Kiddie. Script Kiddies routinely browse security websites looking for exploits disovered by other people and uses these exploits to deface or hijack vulnerable websites. Skiddos are generally regarded as having very little skill, which is usually contrary to their own deluded belief that they are 1337 (elite).
An administrator of forum X calls little Jimmy a douche. Jimmy searches google for Forum X version 1.2.1 exploits, finds a perl script and uses it to deface the forum.
Jimmy is a skiddo.