It's when a girl shits, and qeafs at the same time, hince the name, sheaf.
Ewwwwwwwwww, she just sheafed!!!
1. When a female sharts out of her lower female privates
2. A shart out of a female lower private
1. Preston: "I think my sister just sheafed her pants !"
2. Preston: "Awww! I smell a sheaf!"