something forbidden or prohibited; a taboo (historically referred to prohibitions by authority)
社内での個人的な取引はご法度だ。
Personal business transactions within the company are forbidden.
その話題はこの家庭ではご法度になっている。
That subject is taboo in this family.
江戸時代にはいくつかの行為が御法度とされた。
In the Edo period, several acts were designated as forbidden.