Shatterproof is a term used in fluorescent lighting that denotes strength and quality of the bulb. It means that under normal circumstances and usage, the bulb is not going to shatter and break. Of course, in extreme circumstances, and through misuse, the bulb may still break. One can also find guards and covers that are shatterproof that can protect the bulb further. Because these types of bulbs contain mercury, which is not safe to breathe, it is a good idea to choose shatterproof bulbs and always to handle them with care. When around mercury and other dangerous things, it is always best to err on the side of caution.