When he gets pig-headed, even his dad can't do anything about it.
Tips
memory
Look at the character: 强 (strong) sitting on top of 牛 (ox / cow). A 'strong ox' — that is, an animal that won't budge no matter how hard you push. That's exactly what 犟 means as a personality trait.
register
犟 is colloquial and slightly negative. It overlaps with 固执 (gùzhí, 'stubborn'), but 犟 is earthier — it's the word a frustrated parent or grandparent uses about a child who refuses to back down.
