"UFO Wave refers to the gradual or sudden increase of UFO sighting reports in a certain geographical area for a certain period of time".
 Ahmad Jamaludin and Robert Bartholomew, UFOs Over Malaysia & Southeast Asia.
( to be published).

"A UFO wave in the broadest sense is any notable and temporary increase in sighting reports above the usual rate"
Thomas E. Bullard, Waves, International UFO Reporter, Vol. 13, No. 6, Nov/Dec. 1988.
 

" Flaps are the combined products of concentrated UFO activity or periodical surges of sightings and with a sudden outburst of publicity".
Richard Hall (ed.), The UFO Evidence, NICAP, May 1964.

" A UFO  wave is an unexplained increase in the number of UFO sighting reports over a certain  period of time. The number of  sightings reported builds to a peak and thendecreases to normal, prewave levels".
 David M. Jacob, UFO Waves, The Encyclopedia of UFOs, Doubleday & Co., Inc. NY, 1980

Comment

When UFO sightings or manifestations increases in a certain area, the Americans initially called it a "flap". A flap however, usually denote a concentration of UFO sightings in a small area. But looking on a global scale, the word "waves" is more suitable as it shows the magnitude and intensity of the concentrated reports over a wider area.