Dictionary.com
definitions

delta wave

noun Physiology.
  1. any of the slow brain waves constituting delta rhythm.

Origin of delta wave

First recorded in 1935–40
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
delta wave in Medicine

delta wave

n.
  1. A slurring of the R-wave upstroke in an electrocardiogram as seen in Wolff-Parkinson-White syndrome.
  2. delta rhythm
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.