Wiktionary
vb. (context idiomatic English) To use every means possible to overcome a difficult opposition
Usage examples of "fight tooth and nail".
Given a chance, Frank would fight tooth and nail for the D-G's chair.
The ego is insatiable, and will fight tooth and nail against surrender, against its own limits.
A system that will fight tooth and nail on its own against any possible would-be conqueror.
If she was going to fight tooth and nail, down to the last moments, then he would let her.
And she would, Audrey had discovered, fight tooth and nail to preserve the sanctity of her rational world.
This was most decidedly Mr Lawrence's opinion He was a tall, dark man who not only looked and sounded very well in court but who also had a reputation for defending his clients with the most dogged tenacity, rather as some medical men fight tooth and nail for their patients' lives, making a great personal point of it He was not one to stand on his dignity nor on legal etiquette and after the first meeting in his chambers with Jack's solicitors he often saw Stephen informally, all the more so since they took to one another at once They had both been to Trinity College in Dublin, and although they had scarcely met there they had many acquaintances in common, they were both ardent champions of Catholic emancipation, and they both detested Lord Liverpool and .