(il est) maigre comme un clou : (he is) as thin as a rake
un clou : a nail (made of metal)
Now that you know how to translate 'Maigre-comme-un-clou' in English, why not go further and test our online French course for free?
What our users say:
Test your French with Frantastique today and get a free level assessment.
Absolutely free - no strings attached.