수시로 + verb: 수시로 확인하다, 수시로 연락하다
frequently, at any time, whenever needed
Example
비밀번호는 수시로 바꾸는 것이 안전합니다.
It's safer to change your password frequently.
Word parts
수 follow+시 time
Literally 'following the time' — whenever the moment calls for it.
Good to know
Also used in college admissions: 수시 (rolling/early admission) vs. 정시 (regular admission).