1. The act of chewing up food and spitting it into another's mouth. This is commonly done for those who lack salivary glands, therefore they would have some difficulty chewing up dryer foods such as bread, pancakes, or cupcakes.
2. A sexual act in which a male partner defecates into the mouth of the other partner, then proceeds to masturbate onto the feces. The first partner chews up the feces and cum into a mush. The partner then drops the mixture from their mouth into the other partner's mouth, just as a mama bird would do to feed her young.
1. Dan doesn't have any saliva, so Sarah had to mama bird him that cupcake.
2. Roger loves shit so he wanted Randy to give him a good old mama bird.