General synonyms:
* Postponed
* Deferred
* Procrastinated
* Held up
* Put off
* Suspended
* Stalled
* Set back
More specific synonyms:
* Late: If the delay is about timing.
* Backlogged: If the delay is due to a large volume of work.
* Behind schedule: If the delay is about a project or timeline.
* Arrested: If the delay is about movement or progress.
* Impeded: If the delay is caused by an obstacle.
* Lagging: If the delay is about something that is falling behind.
* Slowed down: If the delay is about a reduction in speed.
The best synonym will depend on the specific situation you are describing.