pothead vs. stoner

pothead

noun

Slang.
  1. a person who habitually smokes marijuana.

stoner

noun

  1. Slang. a person who is habitually high on drugs, especially marijuana, or alcohol; a person who is usually stoned.
  2. a person who pelts or assails with stones:

    stoners of Paul the Apostle.

  3. Chiefly British. a person or thing that weighs a specified number of stone (used in combination):

    a 12-stoner.