A warren is a network of underground tunnels and burrows where rabbits live together in a colony. Wild rabbits dig these elaborate systems of connected passages, creating a hidden neighborhood beneath fields and hillsides. Each warren has multiple entrances and exits, living chambers, and escape routes, like an underground apartment complex designed by rabbits.

The word can also describe any crowded, maze-like place where people live or work close together. You might hear someone describe a confusing office building with endless hallways as a warren of cubicles, or call a densely packed neighborhood a warren of narrow streets. The image is always the same: lots of tunnels, passages, or pathways branching off in different directions, creating a space that's easy to get lost in.

A famous fictional warren appears in Watership Down, Richard Adams's novel about a group of rabbits searching for a new home. In the story, different warrens have different cultures and rules, just like different towns or cities might.