What is the definition or description of: swollen foot?

Swollen foot: Just means fluid is collecting in the tissues. When only 1 foot is swollen, it usually means the cause is local (something going on with in the foot), but if both feet are swollen, it usually means your body is retaining fluid, and the only reason it's showing up in the feet is that gravity thing. If you stood on your head all day, your head would swell.

See below: It is inflamation with retention of flood causing an increased size of the foot.