be (as) strong as an oak

1. To be extremely durable or hardy in construction; to be able to withstand a lot of stress or rough use. I was apprehensive when he said he was going to build the house himself, but the whole structure is as strong as an oak! Don't worry about dropping that end table—it's strong as an oak. I was surprised that our tent proved to be as strong as an oak during that windy storm.

2. To have or display extremely robust physical health or strength. Due to a lifetime of physical labor, my father is strong as an oak. My grandmother exercises every day and always eats a balanced diet, so even in her 80s, she is as strong as an oak. Our father was always as strong as an oak, so it took us all by surprise when he was hospitalized by a heart attack at the age of 48.

3. To have or exhibit uncompromising and indomitable resolve, spirit, and strength of character. He was strong as an oak in negotiations, so he always got what he wanted. During such times of hardship, this country needs a leader who is as strong as an oak. A: "I can't believe Vanessa is still so positive and upbeat after that horrific accident." B: "I know, she's strong as an oak."