The term "mecha musume" was first used for a series of figurines produced by the japanese company Konami. The figures personified old military vehicles, such as tanks and planes, as cute girls. It's not used to refer to a general art style in which the features of historical military warcraft, or more fanciful science fiction mecha designs. The term means, literally, "mecha girls."

(noun) A successful type of theft which results in an acceptable, impressive and rewarding payday for the protagonist.