Is there a difference between 回转 and 掉头?
回转 = "rotate" e.g. "1000rpm" means "rotate 1000 times per minute" = "每分鐘回转1000 次"
  
  回转 (至相反方向) = "rotate to opposite direction" = "turn 180°/ turn around"


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  调头 = "turn around" (to the opposite direction)
  
  掉头 = "turn one's head; turn around"


调头 and 掉头 are interchangeable when it means "turn around" But 掉头 can mean "turn one's head" in different context