Use errant to describe actions that deviate from accepted standards or rules. The team disciplined the errant player for breaking the curfew.
Pro Tip 2/3
Negative connotation
Errant often implies a moral or ethical lapse rather than a simple mistake. His errant ways led him to clash with the law.
Pro Tip 3/3
Expressing correction
When correcting someone's 'errant' action, it suggests they significantly veered off course. The manager addressed her errant employee's behavior in the meeting.