Adverb
Secretly; in private; insidiously.
Source: Webster's dictionaryBetter speake truth rudely, then lye covertly. George Herbert
he did it covertly Source: Internet
"As evidenced by the Snowden leaks, the United States has been covertly accessing telecom networks worldwide, spying on other countries for quite some time," the spokesman said. Source: Internet
An Army special operations team is airdropped into Japan to support covertly inserted Comanche helicopters. Source: Internet
A group of FSB officers were covertly inserted into Rodchenkov’s doping control team. Source: Internet
Blondlot repeated his most recent experiments and got the same results—despite the fact that Wood had reached over and covertly sabotaged the N-ray apparatus by removing the prism. Source: Internet