2.nounA thing used to erase or remove something written or drawn by a pen or a pencil.
"I have worn out the eraser on this pencil."
3.nounA thing used to erase something written by chalk on a chalkboard, by marker on a whiteboard, or by some other erasable implement; a chalkboard eraser, whiteboard eraser, etc.
4.nounAn overwriter program used to prevent data recovery.