On Hold Meaning

(idiomatic) Delayed; postponed; suspended.

Example:   This project is on hold until we can get more information.
Waiting on a telephone call.
  I have been on hold for 45 minutes listening to a recording about how important my call is to them.
On reserve; being held for someone.
  I have a book on hold for me at the library.
Pertaining to a telephone hold state.
1999, New scientist:
  Now James Kellaris, a professor of marketing at the University of Cincinnati, reports that the sexes respond differently to onhold music.