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.
A delta is often a patchwork of marshes, swamps, lakes, and tidal flats (muddy or marshy areas that are covered and uncovered by the rising and falling tides). During the normal flow of the main river in a delta, all the water is guided out to the ocean by the active distributaries.rcuate deltas are the commonest form of delta. They are fan-shaped, with the wide portion of the fan farthest from the mainland. Crossed by many short, well-defined distributaries, these types of deltas are composed of relatively coarse sediments.