A stock unit is a term used to describe the ownership of a company. It is composed of four parts: STEER (5 letters), COW (3 letters), SHARE (5 letters), and str (3 letters). STEER refers to the leadership of the company, COW is a reference to the financial resources of the company, SHARE is a representation of the ownership of the company, and str is an abbreviation for the stock market. Together, these four components make up a stock unit, which is a measure of ownership in a company.