The term 'street runner' is used to describe someone who is a fast and agile runner, usually in an urban environment. The crossword solutions for this term are SKI (3 letters) and GAMIN (5 letters). SKI is a type of winter sport that involves sliding down a snow-covered slope on skis, while GAMIN is a French word meaning a street urchin or a mischievous child. Both of these words can be used to describe someone who is a street runner, as they both involve agility and speed.