Definitions for "Blow-in"
A subscription promotion card blown loosely into a magazine so that it will fall out and attract attention. Paid and controlled titles use blow-ins primarily as an ongoing source of new business.
Printed insert - usually a postcard or a double postcard - blown into a catalog as the catalog comes off press
The act of inserting business reply cards or other printed matter loosely into a publication. So named because they are literally blown into the publications by a machine prior to mailing.
a stranger who appears unexpectedly.