Mecha Musume (メカ娘)
Mecha Musume (メカ娘, Mecha Girl) is a series of mecha girls figures designed by Fumikane Shimada and based on real weapons.
Konami has developed the series and released them as trading figures.
Mecha Girl as proper noun and trademark
Konami applied for the term as its trademark when it launched Mecha Girl (Mecha Musume) as a figure, so if you respect trademarks, it would be a misuse to use this tag for anything other than Fumikane Shimada's anthropomorphic weapon girls.
However, the term "Mecha Musume" had been used before Konami's trademark registration, so this perception is not necessarily a common one.