1. When something is "fancy", "posh", expensive, luxurious or just damn great.
2. Conversely, the word can be used ironically to have to opposite meaning, this stating something is "Deetjens" can also mean it is crappy, low rent or poor quality.
Origin: The term is named after the Deetjens Big Sur Inn in California and entered the lexicon simulatneaouly meaning "posh" and "crappy" when a group of young people were denied entry there. Hence forth the name of the hotel took on this meaning and the use of the term spread.
2. Nagative: "This flat has rats in the walls. Deetjens!"