Core terms
Runner
Slang for a stock making a large, sustained move, sometimes over several sessions. There is no defined threshold.
A runner is usually a small cap that keeps rising after its first big day, often on a catalyst that keeps attracting attention. Traders watch whether it holds above key levels on the second day and when the first down day comes.
The label is applied in hindsight. Many stocks that look like runners on day one give back most of the move on day two.
What traders should verify
Compare a runner's day-two behavior with base rates rather than with the few memorable examples.
Do not conflate
Trader usage; no official definition.
Primary source
Trader usage: there is no official definition, and platforms and tools may calculate it differently.