I fell on my tailbone.....Hematoma?

Hematoma = pooling or severe leakage of blood, aka bruise, and usually some sort of localized swelling too. Perhaps Gallop will chime in here with her medical knowledge. I only know from my own and my horse's injuries.

The horse had a swollen area a little bigger than l could cover with my hand, just below the point of her rump. The vet said it was hematoma, a pooling of blood between the layers of fascia, between skin and muscle.

I've had two diagnosed hematomas

(hematomae?). One was from a very bad buck-off. My friend who witnessed it said that I was 3 feet above the saddle when I started to come down. Apparently the medial side of my knee hit the cantle on the way down. It blew out a blood vessel and most of my lower leg filled with blood - one doozy of a bruisey! As it healed, it went through some technicolor stages. My husband called me his colored girlfriend, as the various colors shone through my pale skin.

The other one was a result of a mini donkey resisting getting his hooves trimmed. He kicked out and nailed me inside my wrist. It popped up immediately like a purple half-egg and scared the stuffing out of me. That one resolved within a couple of days, but I got ice on it within 10 min.

If you don't have a bruise, you don't have a hematoma (in my non-medical opinion).