â¢ FLANK (noun). The noun FLANK has 4 senses: 1. the side of military or naval formation. 2. a subfigure consisting of a side of something. 3. a cut from the fleshy part of an animal's side between the ribs and the leg. 4. the side between ribs and hipbone. Familiarity information: FLANK used as a noun is uncommon.