Luff

From KiteWiki

Luffing is when your kite loses its shape and tumbles out of the sky, usually because you flew it too close to the edge of the wind window or flew it over your head. It is agrevated by gusty conditions and low aspect (squarer shaped) kites suffer from it less that high aspect (long thin) kites.

Once a kite has luffed, it often tumbles to a position straight downwind of the pilot, only to open out directly downind where it re-inflates and generates the most power. The unprepared pilot may then face plant or superman.