1. In a stealthy, sneaky, or clandestine manner; done secretly or furtively without being noticed
He surreptitiously entered the building through the back door.
Ele entrou sub-repticiamente no edifício pela porta dos fundos.
2. In a way that is intended to escape attention or detection
She surreptitiously removed the documents from the office.
Ela removeu sub-repticiamente os documentos do escritório.