Tough as Nails humorous informal slang
Having great strength of body, mind, or will, and resilience in the face of hardship or pain
Don't think that she's old, she's still as tough as nails!
At home, she is a warm-hearted and sweet girl. But at work, she is as tough as nails!
Because her family is so poor that her parents cannot afford the high costs of education, she has to work and study at the same time. She is as tough as nails!
The top quality
1. Good or fantastic
2. (of a person) Attractive, or sexy
3. A sexually attractive person
Someone or something is so good or successful that it's impossible for anyone or anything who comes after them to follow.
In flawless condition
Used to refer to something one's good or skilled at.
This idiom can be considered to derive from the 1860s. In the early 1800s, it was not "tough as nails" but it was "hard as nails". Nowadays, people use both equally.
To do something in an unusual way
I guess I like to run against the grain in everything I do.