a specified majority of votes (that exceeds the simple majority) needed to approve a motion
supermajority in American English
(ˌsupɛrməˈdʒɔrəti; ˌsupɛrməˈdʒɑrəti)
noun
a specified number or percentage of votes, exceeding the minimum needed to produce a majority, required to pass certain legislative bills, ballot issues, etc.