Like fornication but
inside of a fort or fort-like structure.
eg. Blanket fort, tree house, refrigerator
box, etc.
Michelle: I hear Steve and Andrea are building a fort instead of
coming out tonight.
Leanne: Oh yeah? Sounds like they'll be into some serious fortication this weekend.
Michelle:
Truth. If the refrigerator box is a rockin,
don't come a knockin.