Noun
mail consisting of large numbers of identical items (circulars or advertisements) sent to individual addresses at less than 1st-class rates and paid for in one lot
Source: WordNetAs the pandemic worsens, mail usage is slowing down — particularly businesses have cut back on sending advertisements and bulk mail — and the USPS is quickly running out of money to supports its operations. Source: Internet
Yes the ballots are postage paid but the Post Office handles them as 3rd class bulk mail, meaning it is not expedited. Source: Internet