spurt
A sudden, strong burst of liquid or activity.
A spurt is a sudden, forceful rush of liquid shooting out in a stream. When you squeeze a water bottle hard, water spurts out. If you accidentally step on a ketchup packet, ketchup spurts everywhere. A garden hose with a kink in it might spurt water when you straighten it out. The key idea is that the liquid comes out quickly and forcefully, not in a gentle trickle.
The word also describes a sudden burst of activity or growth. A runner might save energy for most of a race, then put on a spurt of speed near the finish line. You might experience a growth spurt where you suddenly shoot up several inches in just a few months, leaving your pants looking too short.
As a verb, to spurt means to shoot out suddenly in a stream, or to increase suddenly for a short time. Water can spurt from a hose, and a runner can spurt ahead near the end.
When something happens in spurts, it comes in irregular bursts rather than steadily. A student might work in spurts, concentrating intensely for twenty minutes, then taking a break, then working hard again. Rain that falls in spurts stops and starts unpredictably throughout the day.
The word captures that sense of suddenness: whether it's liquid shooting out or energy bursting forth, a spurt happens quickly and usually catches you by surprise.