Definition: a deviation from a direct course or the usual procedure
Encountered from A Literary Visitor Strolls in From the Airport by Charles Mcgrath.
But he was disappointed that on this route the city offered no dramatic prospect of itself, not even when he detoured up Mount Prospect in Mount Prospect Park. “It really should be called Ex-Prospect Park,” he grumbled.
I understand this word now because he took a long way up the mount prospect park and nothing is happening.