Triphasic waves is an old term, and does not exist as an entity on its own in the new ACNS 2021 guidelines.The new terminology is "Generalized periodic discharges with triphasic morphology". The new definition puts less emphasis on the morphology of discharge, and more emphasis on periodicity itself...

Fernández-Torre and Kaplan, PMID 34155183. While clearly the periodicity/rhythmicity and focality of a discharge, triphasic or not, are the most important features to note, an interesting review in the Journal of Clinical Neurophysiology (above) posits that there is a "typical" and "atyp...