Definition of "gremlin"

(originally Britain, aviation, Royal Air Force slang)

1. (obsolete) A contemptible person.

2. An imaginary creature reputed to be mischievously inclined, for example, to damage or dismantle machinery.  quotations  examples

   Quotations

   • Crucial time was saved by the fact Nexus didn't require a Transport & Works Act. Nevertheless, other gremlins kept raising their heads.

     2023 November 29, Richard Foster, “Tyne & Wear Metro goes with the flow”, in RAIL, number 997, page 34

(by extension)

1. Any mysterious, unknown source of mischief or trouble, or the problem created thereby.  examples

2. (surfing, skateboarding, slang) A young, inexperienced surfer or skateboarder, regarded as a nuisance.