refrain from voting
"Many eligible citizens chose to abstain from voting because they felt the candidates were equally unqualified."
Keep or withhold oneself.
"During the vote, several members chose to abstain rather than support either side of the debate."
The word "abstain" comes from the Latin phrase abstineō, meaning "to hold oneself back." It entered English via Old French and Middle English, combining the prefix abs- (from) with teneō (I hold).