- a seven-inch phonograph record played at 45 r.p.m., especially a popular-music single: She’s in the market for a phonograph so she can play her grandfather’s mint collection of 45s from the 1960s.
- an identifier of or nickname for Donald Trump, the 45th U.S. president, alternately used with disparaging intent by opponents and with affection by supporters.
- a pistol, revolver, or cartridge of .45-caliber, or having a diameter of .45 inch.
