When I answered that it is a function that takes a function as a parameter, or like in JavaScript - a function that returns a function - I was told I was wrong. They had a spiel that it was to do with LINQ aggregation or something. Really?...wait what. Oh ok. Better check your facts guys - it's pretty embarrassing to tell interviewees they are wrong based on your mis-guided beliefs. Come to think of it, this would be the first interview I've ever had where they tell you your answer is wrong. An interview with a normal organisation will note something down and move on to the next question without a word (at least in my experience).