noun
the normal brainwave in the encephalogram of a person in deep dreamless sleep; occurs with high voltage and low frequency (1 to 4 hertz)
• Syn: ↑delta wave
• Hypernyms: ↑brainwave, ↑brain wave, ↑cortical potential
* * *
the normal electrical activity of your brain when you are asleep
Useful english dictionary. 2012.