Those who don’t “cover their ass” show how vulnerable they are. Or they don’t have to hide their disadvantage, such as “The Fool” in early Tarot decks. According to Freud, infantile sexual symbol.... Little Giant Encyclopedia
The meaning of this dream varies according to its details, but it is a generally good omen.
Whether the buttocks were your own or someone else’s, you can anticipate happy times ahead.
If they were animal buttocks, the indication is of financial luck.
If the dream involved being kicked in the buttocks, you can be sure of a steady rise in status; but if you did the kicking, you will have to cope with some foolish jealousy in your immediate circle.... The Complete Guide to Interpreting Your Dreams
This part of the body is typically a bad sign. Whether they are beautiful or deformed and drooping, they augur all kinds of nasty remarks and humiliations. In the first case, it warns of a possible cheating partner; in the second, of an embarrassing action. ... The Big Dictionary of Dreams