1. A piece of cloth or similar material, typically oblong or square, attachable by one edge, used as the symbol or emblem of a country or institution or as a ball in a game
The flag of Brazil has a green background.
A bandeira do Brasil tem fundo verde.
2. To become tired or less energetic; to droop or lose strength
My energy began to flag after lunch.
Minha energia começou a diminuir após o almoço.