your/somebody's number two
1. One's second-in-command; the person with the second-highest level of power or authority in some group, company, or organization. He left his number two in charge while he traveled abroad to seek new investors. This promotion will actually make me the new number two in the company.
2. A euphemism for defecation ("number one" being a euphemism for urination). Do you have to do a number one or a number two?
your/somebody’s number ˈtwo(informal) the second most important person in a company, an organization, etc: Brian Jones is the new number two at the ministry.
n. defecation; an act of defecation. Mommy! I gotta do a number two.