Dysphemism

The latter is generally used more often in the sense of something deliberately offensive, while the former can be either offensive or merely humorously deprecating. Examples include the American military's use of "shit on a shingle" for their common breakfast of creamed chipped beef on toast, or "dead tree edition" for the paper version of an online magazine.

Oddly, some humorous expressions can be both euphemistic and dysphemistic depending on context: for example "spank the monkey" might be used as either a softer alternative to "masturbate", or as a more deliberately provocative one depending on the audience.