Толстый зад нашего учителя не помещался на стуле. | Our teacher's fat ass wouldn't fit in the chair. |
Тётка заслонила проход своим широким задом. | The woman blocked the way with her big wide ass. |
NB When the word зад functions as a subject and has no descriptive modifier, the construction зад у + Genitive is often preferred to (a) and (b), above: | |
Зад у Петьки был худой и костлявый. | Pet'ka had a skinny, bony butt. |