To ingrain something in one's mind through constant repetition. A noun or pronoun can be used between "din" and "in." When your mother and I were kids, our teacher simply dinned the multiplication tables in over and over until we could remember them. The manager always dins in the same motivational catch phrases whenever we have a staff meeting.
See also: din
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.