a downhill race over a winding course defined by upright poles
"The skier won the slalom after weaving expertly through the tightly packed gates at the bottom of the mountain."
The sport of skiing in a zigzag course through gates. (Often used attributively)
"She spent hours practicing her slalom technique to master navigating the tightly packed gates at high speed."
race on skis around obstacles
"The skier had to maintain perfect balance while weaving through the poles in the slalom course."
To race in a slalom.
"The skier launched off the starting gate to race through the trees during the downhill slalom."