Any container, made of any substance, utilized to house or hold a pet.
Husband: "We'll have to move Ollie's cage..."
Wife: "For the last time, it's not a cage, its a Crate!"
Husband: "Have you seen this? This is a cage if I ever saw one!"
Wife: "No, it's a crate."
Husband: "This is not a crate. Crates are the wooden boxes dinosaurs come in."
Wife: "Only an idiot would trust a dinosaur to stay in a wooden box."