Hueso duro de roer

a tough nut to crack; **a tough nut to crack**; **a hard nut to crack**; **a formidable opponent**; **a difficult challenge**; **a tough customer**

Hueso duro de roer means a difficult person, a tough opponent or a challenging problem that is not easy to defeat, convince or solve.

It often carries a tone of respect for the difficulty involved.

• strong competitors
• stubborn people
• difficult negotiations
• complex problems
• demanding challenges

The expression comes from the obvious physical difficulty of chewing a very hard bone.

Just as an animal must make a great effort to break such a bone, people must work hard to overcome certain obstacles or opponents.

The metaphor has existed in Spanish for centuries and remains highly transparent.

The expression is often complimentary rather than insulting.

Calling someone un hueso duro de roer usually recognises their determination, intelligence or resilience.

For that reason, it frequently appears in politics, business and sport.

Spanish often uses food-related metaphors to describe difficulty:

• Hueso duro de roer → a tough nut to crack.
• Pan comido → a piece of cake.
• Estar en su salsa → to be in one's element.

Interestingly, English and Spanish choose different foods—bones and nuts—to express essentially the same idea of something difficult to break through.

This idiom has an almost perfect English equivalent.

Translate it naturally as:

• a tough nut to crack
• a hard nut to crack

Depending on the context, you may also use:

• a formidable opponent
• a tough customer
• a difficult challenge