When you have no time, are unprepared, or don't know what you're doing... You're pulling it out of your ass. Commonly used in situations where a person may have procrastinated or waited until the last minute to prepare anything, or is put in position where they must perform or answer questions on things they have no idea about.
My boss just came and asked me for a summary of customer info and I had to pull it out of my ass.
a fun thing to say to people when they piss you off or you dont like them anyway. Adding the 'bitch' on to the end is for emphasizing the phrase, therefore giving it more strength and effect.
Trent Lott: Ah think thayt the Seperatist Parrty wuz a gooood thang!
Me: Kiss my ass bitch!