Rashi: It covers and wraps the entire body, over all garments.

Radak: When they see that their intent for me will not be fulfilled, they will be cloaked in shame.

Malbim: Kelimah is from others; Bushah is from oneself. The Levush is below, and the Me'il covers. Normally, one is Lovesh Bushah and Oteh (covers himself) with Kelimah. David requested oppositely, that the Kelimah not be above, external to the garments, like one who feels shame without reason, rather, like a garment fitted to his body. It is a true Kelimah. Also the Bushah should not be an inner garment that only the wearer sees, rather, like an outer garment that is exposed.