At the risk of sounding like a doofus
I never considered HuCARDS cartridges. Any cartridge I've seen, up to the N64, were big clunky P.O.S. that you had to blow on to get them to work properly. I always go by the saying "If it walks like a duck and talks like a duck..." - the HuCARD does neither. It's its own thing. Sure it performs the same function, but so do CDs. The SMS is a perfect example -they didn't call both game formats cartridges. They called the main cartridges "cartridges", and the cards "cards".
Basically, I look at Turbochips and Sega Cards as completely different formats from cartridges and CDs. However, technically they are cartridges. Wiki explains cartridges as:
In various types of electronic equipment, a cartridge can refer one method of adding different functionality or content (e.g. a video game cartridge), or a method by which consumables may be replenished (e.g. an ink cartridge for a printer). The term cartridge tends to be applied loosely to a large range of techniques which conform to this general description.
In general, the term tends to mean any detachable sub-unit that is held within its own container. The term cassette has a similar meaning. A video game cartridge may also be referred to as a cart or game pak.
Now, I've never called a cassette tape a cartridge and I would look at anyone strange for calling it that. It may by broad definition be a cartridge, but no one calls them cartridges. I tend to see HuCARDs in that way. Technically, by definition, they are cartridges, but we all know they are something else, and better.
By most definitions of cartridge, CDs also fall under that category. CDs are inserted into a bigger instrument and are easily replaceable. I guess MiniDiscs would more easily fit the cartridge definition than just regular CDs since they are encased; however, it's still just a CD in a plastic case. So is it just the plastic case that makes it a cartridge?