Layer III audio can also use a "bit reservoir", a partially full frame's ability to hold part of the next frame's audio data, allowing temporary changes in effective bitrate, even in a constant bitrate stream. Internal handling of the bit reservoir increases encoding delay.[citation needed]

Answer this question, if possible (if impossible, reply "unanswerable"): A partially full frame's ability to have part of the next frame's audio data is referred to as what?
bit reservoir