1. a mischievous creature imagined to cause malfunctions in machinery or equipment
Usage: informal; often used humorously or as a scapegoat for unexplained problems
2. a source of trouble or malfunction; something that causes problems
Usage: informal; used metaphorically to explain technical or mechanical failures

Examples

• The engineers blamed a gremlin for the computer crash.
• There must be a gremlin in the system—nothing is working right today.
• The old car kept breaking down; we joked that gremlins lived in the engine.
• Software developers sometimes joke about gremlins when they can't find the source of a bug.
• The printer jammed again—I think there's a gremlin in it.
• After the power outage, we suspected gremlins had caused the equipment failure.