Pronunciation: (ôf'glīd", of'-),[key] —n.Phonet. 1. a transitional sound produced as the vocal organs move from a previous speech sound to an inactive position or to the position of a following sound. Cf. on-glide. 2. the final, weaker part of a complex vowel, such as a diphthong, as the (i) sound of the (oi) in boy.