Irregularity
Irregular, Disorderly
noun, な adjective
You know that 規則 means "rule" or "regulation." So a not "rule" or "regulation" is an irregularity.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
私の仕事は時間が不規則です。
My work hours are irregular.
寝る時間が不規則なのは良くないよ。
It's not good to have irregular bedtimes.
不規則な生活で体調を崩してしまった。
My health was ruined by my disorderly life.