Standby means you are required by your employer to be prepared to report immediately for work if the need arises, although the need may not arise. According to RCW 41.37.010:
Wash. Admin. Code § 415-106-225
Statutory Authority: RCW 41.50.050(5) and 41.37.010(6). 08-02-046, §415-106-225, filed 12/27/07, effective 1/27/08.