Definitions

1. noun

A tuft or tufts of hair hanging down from the back of a horse or other animal, or a similar tuft or tufts of hair on a person, especially a child.

“The horse’s tagtail was tangled with a piece of twine.”

2. verb

To hang or be hanging in a loose, tangled mass, especially at the back of a horse or other animal.

“The horse’s hair had started to tagtail in the rain.”