A person who gets paid to watch a woman give birth. Doulas have no medical training or schooling, but some are highly trained in the art of emotional manipulation, sometimes coercing the mother into carrying out the doulas fantasy birth. This has resulted in putting mothers in danger if they take misleading doula advice. Doulas are not meant to be involved with the child; their sole job is to do what the mother asks, such as fetching her a glass of water while in labor. Many doulas are also known to have strained relations with their mother, and some doulas attempt to overstep their boundries with the new child. Many doulas have been banned from well-respected hospitals due to their interference with life saving procedures.

Somebody close to you. A good friend. Probably derives from the real word doula that refers to somebody who is there for a pregnant woman emotionally and physically through her pregnancy. In the slang tense it is somebody who's there for you that you can always count on.

Someone who breastfeeds for the mother after pregnancy. See Wet Nurse.
Also, slang: male with prominent man boobs.