Definition of "run-in"

run-in¹

noun
plural run-ins
1. An encounter; a scrape or brush, especially one involving trouble or difficulty.
  Quotations
  During that time he had two more run-ins with the law. One involved the sale of stolen property. The other was for a series of hot checks.
  2004, Pamela Morsi, Suburban Renewal, page 95
2. The end-phase of a competition.

run-in²

adjective
not generally comparable, comparative more run-in, superlative most run-in
1. (participial adjective; editing, typography) (not comparable) Having been run in before or behind previous text.
2. (participial adjective; mechanical, engineering) (sometimes comparable) Having been run in to seat the parts.