coriace

Tom est coriace.

Tom is tough.

Je sais que Tom est coriace.

I know Tom is tough.

Le filet provient d'un muscle qui est peu sollicité, il n'est donc pas coriace.

The tenderloin is cut from a muscle that does not do much work, so it is not tough.

Il paraît tendre en surface, mais au fond, il a une volonté de fer qui fait de lui un négociateur extrêmement coriace.

He seems like a softy on the surface, but at the core he's got an iron will that makes him an extremely tough negotiator.

Je sais que Tom est un type coriace.

I know that Tom is a tough guy.

Tom était un adversaire très coriace.

Tom was a very tough opponent.