lacking in insight or discernment; "too obtuse to grasp the implications of his behavior"; "a purblind oligarchy that flatly refused to see that history was condemning it to the dustbin"- Jasper Griffin
a characteristic language of a particular group (as among thieves); "they don't speak our lingo"
informal language consisting of words and expressions that are not considered appropriate for formal occasions; often vituperative or vulgar; "their speech was full of slang expressions"