It is a slang term used to describe a baby. Usually this term is for a young teenage woman who happens to have a child, or a woman with a low income supporting a child or several children. This isn't limited to females only, a couple, or a single male can also have fall into this category. Meal tickets regard to the fact that a child or baby, are considered a "ticket" to buying a meal, or another mouth to feed.
Did you know that Stephenie just had a kid?? Yea, that sucks, she just got herself a free meal ticket!