Roost/ruːst/ Definition 1 of 4Pro Tip 1/3Physical Locations Refers to actual places where animals sleep; not used for humans. The naturalists found an eagle's roost high in the mountains. Pro Tip 2/3Safety and Security Suggests a roost is typically a safe, comfortable place for birds or bats. The bats found a roost away from predators inside the cave. Pro Tip 3/3Habitual Action Animals often use the same roost regularly, demonstrating habit. Swallows returned to their roost under the bridge each evening.