The Dusty tipewriter in the attic is old as the hills definition

The phrase means that the dusty typewriter in the attic was exceedingly old.

Explanation:

"As old as the hills" is an expression that is used to define something that is very or exceedingly old. The phrase sometimes is used for exaggerating things. The phrase has been derived from a book of the Bible.

The given statement is stating that the typewriter found in attic is very old. The particles of dust that sits on the body of the typewriter already suggests that the typewriter is old, but the phrase "old as the hills" is used to exaggerate the oldness of the typewriter, to propose that the typewriter that lies in the attic is ancient.