The original sale of a new security issue from a company to investors/shareholders. Proceeds from a primary distribution are sent directly to the issuing company. All bond offerings are considered primary distributions.
Also sometimes referred to as a "primary offering".
Taobiz explains Primary Distribution
A "secondary distribution" is the opposite of a primary distribution and refers to an occurrence where an existing shareholder sells a block of previously-issued stock and takes the proceeds from the sale. A company only receives funds for a primary distribution, or IPO; the stock continues to trade after the initial offering, but the funds are exchanged between buyers and sellers.