Distal: The more (or most) distant of two (or more) things. For example, the distal end of the femur (the thigh bone) is the end down by the knee; the end more distant from the torso. The distal bile duct is the far end of the cystic duct, the end away from the gallbladder. And the distal lymph node in a chain of nodes is the most distant one. The opposite of distal is proximal.
For a more complete listing of terms used in medicine for spatial orientation, please see the entry to "Anatomic Orientation Terms".