What do you call a trip taken for fun or relaxation?

A vacation is a time specifically set aside for enjoyment or relaxation, like a dream vacation to Hawaii. Vacation began as an Old French word, meaning "freedom or release" from an activity or occupation — like summer vacation. There's no school. During summer vacation, you'll do lots of things — but you won't be in school. You might even go somewhere for a vacation. Another meaning of vacation is "voiding something legal," like the vacation of the old law about not tying your horse in front of City Hall.

Source: Vocabulary