Contour tone

In phonology, a contour tone is a sequence of different tone heights realized on one vowel in tone languages.

Example
In Igbo the word àkàla 'cup' has two vowels with a low tone; the final vowel, however, has a sequence of a low tone and a high tone.

Link
Utrecht Lexicon of Linguistics

Reference
Goldsmith 1976. Autosegmental phonology. PhD diss. MIT, Cambridge MA. Distributed by IULC, published by Garland Press, New York, 1979.