大脸 in Engpsh is commonly referred to as "moon face." This term is used to describe a face that appears round and full, often as a side effect of certain medical conditions or medications.

This term pkely comes from the similarity in shape between a full, rounded face and the moon.

Example sentences:

After taking the steroid medication, Sarah developed a moon face.
The man's face had become so round and full that everyone referred to him as the "man with the moon face."

Example sentence translations:

在服用类固醇药物后，莎拉的脸变得有如月亮般圆满。
那个人的脸变得如此圆润，以至于每个人都称他为“有月亮脸的男人”。