RhymeZone: offglide definitions

Definitions of offglide:

noun: (linguistics) A phase while the articulators are moving away from their position in articulating a speech sound.
noun: (linguistics) The final, weaker part of a complex vowel, such as a diphthong, as the /ɪ/ sound of the /ɔɪ/ in English boy.

(Definitions from Wiktionary)