Answer: No, sort of.
Explanation: While the change in terrain is a key difference, the main one could quite possibly be this-
Walking is generally an exercise that you do outside in an urban or suburban setting, or indoors in a gym on a track or treadmill. Hiking, in contrast, is walking that's done outdoors and along natural terrain. You'll usually encounter elevation changes when hiking, but not necessarily when walking.
However, this is completely opinion based.