Excursion (audio)
Excursion is defined as how far the cone of a speaker linearly travels from its resting position. In general lower frequency drivers or subwoofers are designed to move more air and have more excursion than those of higher frequency. If a speaker is pushed beyond its limits, overexcursion, or "bottoming out", can occur as the voice coil either slips out of the magnetic gap or hits the bottom of it.
Extremes
The MTX Jackhammer, a 22-inch subwoofer made by MTX Audio, is capable of 2.5 inches of linear cone excursion, one way. That's a total range of 5 inches, which is potentially hazardous.