Oscillation was a repetitive movement between different states at regular intervals.
In 2366, after William T. Riker and Deanna Troi escaped from a Ferengi brig aboard the Krayton, Riker attempted to alert the USS Enterprise-D but was denied access to Ferengi communications as all transmissions had to be authorized by DaiMon Tog. Riker then set up a simple oscillation to send out a signal, a message that the Enterprise would understand but the Ferengi would think was normal subspace static. (TNG: "Ménage à Troi")
After entering a subspace distortion in 2367, the Enterprise-D experienced a quantum level oscillation delay which doubled in intensity every 12.3 seconds. Bio-cellular disruption would have been imminent had they not exited the subspace distortion. (TNG: "The Nth Degree")