Shirttail (noun)

The lower edge or hanging part of a shirt, especially when it is not tucked in.

Origin:

From shirt + tail.

Examples:

1. His shirttail was hanging out of his pants.
2. She tucked her shirttail into her pants.
3. The shirttail should be tucked into the pants.
4. He had a habit of leaving his shirttail untucked.
5. The shirttail is the lower edge of the shirt that hangs out.