The person who transgresses — the one who crossed the line. It is the -or noun that goes with 'transgress', built the same way as 'actor' from 'act'. Very formal, and old-fashioned outside two settings. First, religion: 'transgressors' is a standard word in the Bible and in preaching for sinners, and it keeps that solemn ring. Second, law and official rule-writing: notices and regulations sometimes say 'transgressors will be prosecuted', though 'offenders' or 'violators' is far more usual in modern legal English. In everyday speech, nobody says this. You would say 'the person who broke the rule', or 'the offender'. Because it is so formal, writers occasionally reach for it lightly, half-joking, about someone who did something small — 'the transgressor had taken the last biscuit' — and the humour comes exactly from using a grand word for a tiny crime. Recognise it when reading; reach for a simpler word when writing.

違規者、犯戒者；宗教語境作「罪人」「犯過者」。日常英文幾乎不用，中文若要對應日常說法，用 offender（違規者）那一層即可。