千慮 せんりょ いち しつじゃありませんでした
senryono ichishitsujārimasendeshita

Noun
Desu Copula

The polite, past negative form of 千慮の一失

1. It wasn't a mistake despite a thousand considerations.; It wasn't a blunder despite careful thought.

Past/Perfective
Negative
Polite
Terminal Form