Speed refers to how quickly an object moves, or, in more technical terms, the distance traveled per unit of time. In World of Goo, speed refers to how quickly Goo and other objects move; it is similar to momentum. Unlike gravity, speed is not a large factor in creating goo structures, but still plays an important role.
Thrown Goos move at different speeds depending on their momentum.
When detaching a Goo Ball, they tend to try to pick up the pace and go faster so they will not fall of when the Goo Ball is detached. If they try to escape to another node strand and the player remove the Goo Ball before it is done, then when the goo-balls fall off, they move faster up the strands until they are picked up. This is considered a glitch.