First, it is important to note that the term "mongoloid" is considered to be impolite outside of the area physical anthropology.
Within physical anthropology, the term refers to people of East Asia and of the Americas since the natives of the Americas came from East Asia. The most commonly cited features of mongoloids are the shape of their incisors, which are shovel-shaped rather than spatulate, and the existence of the epicanthic fold in their upper eyelids. Mongoloids are also said to have protruding cheekbones and wider and flatter noses. They are also said to be shorter and stockier as an adaptation to cold.
These are some of the most commonly cited traits of "mongoloids" in physical anthropology.