to be something that you know or understand nothing about.

I'm afraid physics will always be a closed book to me. (usually + to)

• cast aspersions on something
• cast doubt on
• cast doubt on something
• cast eye over
• cast eye over something
• casting couch
• cast-iron
• castles in the air
• cast lot with
• cast lot with someone
• cast lot with something
• cast mind back
• cast net wide
• cast net wider
• cast off
• cast off something
• cast pearls before swine
• cast your eye over
• cast your eye over something
• cast your lot with
• cast your lot with someone
• cast your lot with something
• cast your mind back
• cast your net wide
• cast your net wider