dis- 1
a Latin prefix meaning "apart," "asunder," "away," "utterly," or having a privative, negative, or reversing force (see de-, un- 2 ); used freely, esp. with these latter senses, as an English formative: disability; disaffirm; disbar; disbelief; discontent; dishearten; dislike; disown.
Also, di- .
[ bis, Gk dís twice); before f, dif-; before some consonants, di-; often r. obs. des- ]
dis- 2
var. of di- 1 before s: dissyllable.