The Japanese reads 対粛正防御 (tai shukusei bougyo). You can actually hear her say this in one of her stage 3 NP selection lines:
対終末、対粛正防御、はじめ (tai shuumatsu, tai shukusei bougyo, hajime)
beginning anti-apocalypse, anti-purge defenses
対 means anti-, the same as in anti-unit, anti-fortress, etc.
粛正 means enforcement/regulation/purge, the relevant image here is basically some kind of authority forcefully cracking down on something. I go with purge because that’s what Mirror Moon used in their translation of the original Fate/Stay Night when this term came up.
防御 means defense.
The mistake probably came from somehow dropping both 対 and 正, since 粛 on its own can mean solemn.
This is a pretty important term from a lore perspective because in Ea’s description from Stay Night’s status menu (and Zero Material) it’s said that defending against it would need 対粛正/anti-purge armor class.
Obviously it’s kinda late to stop the propagation of this mistranslation, but it’s a cool facet of the lore around Castoria, and especially rewarding for long time fans that read the original Stay Night. It’d be a shame if English-only fans missed out due to a TL mistake.