If a part of your body is swollen, it is larger and rounder than normal, usually as a result of injury or illness.
My eyes were so swollen I could hardly see.
我的眼睛肿得很厉害,几乎看不见东西。
A swollen river has more water in it and flows faster than normal, usually because of heavy rain.
The river, brown and swollen with rain, was running fast.
这条河因下雨变成褐色,水位上涨,水流加快。
Swollen is the past participle of swell.