n.the normal brainwave in the encephalogram of a person in deep dreamless sleep; occurs with high voltage and low frequency (1 to 4 hertz)
同义词：delta wave
英汉双解大词典
delta rhythm(alsodeltawave)
1.
N（名词）
the normal electrical activity of the cerebral cortex during deep sleep, occurring at a frequency of 1 to 4 hertz and detectable with an electroencephalograph δ节律 [physiol] → see also brain wave