gremlin

noun

1. (obsolete)A contemptible person.
2. An imaginary creature reputed to be mischievously inclined, for example, to damage or dismantle machinery.

   “Like Abominable Snowmen, gremlins have never actually been seen; but nobody who works with electronic gear doubts the existence of these mischievous and elusive entities. There are too many malfunctions and failures that can have no other explanation.”

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

3. (broadly)Any mysterious, unknown source of mischief or trouble, or the problem created thereby.

   “We rechecked everything, and we suspect gremlins in the database.”

4. (broadly, slang)A young, inexperienced surfer or skateboarder, regarded as a nuisance.
5. (broadly)A person regarded as similar to a fictional gremlin, in particular: mischievous, troublesome, short, or annoying.

   “Rosa, the main character in Tears of Themis, is also very smart, justice-driven, and willing to help. Meanwhile, the Honkai: Star Rail Trailblazer […] can often be a sarcastic, pessimistic, lazy, self-serving, dumpster-diving gremlin.”