Noun
(phonology) The act or process of constricting or closing the glottis during the production of a speech sound that normally does not involve such constriction.
Examples of glottalization include creaky voice, and the interrupted tones of Vietnamese.
(phonology) Transformation of a consonant into a glottal stop or fricative.
Source: en.wiktionary.orgFor example, high tone in Navajo and low tone in Slavey are due to contrast with the tone triggered by the glottalization. Source: Internet
Miller (2011) analyses the glottalization as phonation, and so considers these to be simple clicks. Source: Internet