Don’t be such a muttonhead and double - check your work.
In a friendly teasing manner, someone might say, “You’re such a muttonhead for forgetting your keys again. ”
A person might use this term to describe themselves, saying, “I can’t believe I did something so muttonheadish. ”
( محاوه، به طعنه، شخص ) خر، گوساله، الاغ، آدمِ بیشعور.