Stretching means making your body longer by moving your joints and muscles. You stretch when you wake up in the morning or after sitting for a long time.
When people say they're stretching, it usually means they're doing some simple exercises to loosen their muscles. This can be anything from touching their toes to bending over backwards to arching their back. Some people also talk about "stretching" themselves as a way of getting more flexible and relaxed - like when you do yoga or Pilates. You might hear someone say, "I need to stretch my legs after that long car ride."
The act by which something is stretched.
