Dissimilation

Dissimilation (also called dissimilatory change) is a sound change in which one sound becomes less similar than another, usually adjacent, sound: Latin peregrinus > French pelerin 'pilgrim', Eng. pilgrim. Dissimilation is the opposite of assimilation.

Dissimilation can be classified according to the same dichotomies as assimilation: partial versus total, progressive versus regressive, contact versus distant.

Example
A famous example of dissimilation is the dissimilation of aspirates in Greek and Sanskrit known as Grassmann's Law.

Other languages
German Dissimilation (de)