Chambers 20th Century Dictionary(0.00 / 0 votes)Rate this definition: Sibilance. sibâ²i-lans, n. a hissing soundâalso Sibâ²ilancy.âadj. Sibâ²ilant, making a hissing sound.ân. a sibilant letter, as s and z.âv.t. Sibâ²ilÄte, to pronounce with a hissing sound.ân. SibilÄâ²tion, a hissing sound.âadjs.
Definition: A delta wave is a type of high amplitude brain wave found in humans. Delta waves have a frequency from one to four hertz and are measured using an electroencephalogram (EEG). These brain waves are thought to emerge from the thalamus and are generally associated with slow-wave sleep (during stages three and four of the stages of sleep.
1 also called delta rhythm, the slowest of several types of brain waves, characterized by a frequency of 4 Hz and a relatively high voltage. Delta waves are deep-sleep waves associated with a dreamless state from which an individual is not easily aroused. Compare alpha wave, beta wave, theta wave. 2 (in cardiology) a slurring of the QRS portion of an electrocardiogram tracing caused by preexcitation in Wolff-Parkinson-White syndrome. Cardiology An EKG finding in WPW syndrome, seen as a slow upstroke of the QRS wave in a background of short P-R intervals See Wolff-Parkinson-White syndrome.