secret ballot

详细解释:无记名投票
【法】 无记名投票, 秘密投票

英语解释：

名词 secret ballot:

a vote in which each person's choice is secret but the totaled votes are public

例句：

The new act stipulates that election to union office shall be by secret ballot of members.新法规定工会职位的选举将由会员秘密投票方式进行。