After every picnic, we give the blanket a thorough shakeout to remove leaves and sand.

shakeout 是由动词 shake（抖动、摇晃）和副词 out（向外）组成的复合动词，字面意思是"抖出来"。shakeout 在这里指通过抖动毯子使上面的杂物（如树叶和沙子）掉落的动作。