Pictures (usually pornographic in nature) that do not have censoring in them. eg. the private parts do not have mosaic censoring, blurring or strikeouts. Sometimes, an uncensored picture may be the edited version of a censored original, done by recreating details that are lost by the strikeout.
In Japan, it is illegal to draw uncensored genitalia if they are to be published publicly for distribution. Some artists skirt around this law by applying translucent strikeouts, which are easier to decensor while maintaining image fidelity. Others maintain a non-Japanese presence to bypass Japanese laws altogether and distribute uncensored versions of their work.