Student or Learner
Moreover, the good news hardly extends to every corner of the country. Violent crime remains extremely high in some troubled cities, such as Memphis and Detroit, and in smaller places such as Oakland, California, and Camden, New Jersey. Most striking is an unexpected spike of gang-related violence in Chicago, where murders are up by 28% so far this year. Against a backdrop of a long-term decline in all crime in the city, as well as a 10% decline for the year, the sudden unrest has caused some alarm.
What does "spike" mean in the above paragraph?
I have checked spike noun - definition in British English Dictionary & Thesaurus - Cambridge Dictionary Online and Definition of spike | Collins English Dictionary but still couldn't get it.