Sorry, my jeans won’t allow my legs to spread any further.
This wildfire might spread to the state of Oregon by the end of this week.
The lavender field stretched out as far as the eye could see.
Remember 広い? Well this is like that, except a verb. When something does the action of getting wide, it means to spread out, to extend, or to stretch.
The reading is the same as 広い, too, so as long as you knew that you knew this reading as well.