an empty
Examples
Erudition - dust shaken out of a book into an empty skull.
An empty head is not really empty; it is stuffed with rubbish. Hence the difficulty of forcing anything into an empty head.
Business underlies everything in our national life, including our spiritual life. Witness the fact that in the Lord's Prayer, the first petition is for daily bread. No one can worship God or love his neighbor on an empty stomach.
An empty belly hears nobody.
An empty bag cannot stand upright.
An empty barrel makes the most noise.