circuit  
noun uk/ˈsɜː.kɪt/ us/ˈsɝː.kɪt/
  (VISITS)         
 C2 [ C ]巡回;巡游;巡回之地 
a regular pattern of visits or the places visited
  They first met each other on the tennis circuit (= while at different tennis competitions). 他们在网球巡回赛上首次交锋。 
 He was a familiar figure on the lecture circuit. 他是巡回讲学中的座上常客。 
  [ C ] law specialized巡回审判区 
a particular area containing different courts that a judge visits
  The judge had served for many years on the northeastern Circuit. 这位法官多年来供职于东北部巡回法庭。 
 a circuit judge 巡回法官 
 - More examples
- He always takes part in the polo circuit.
- We see each other on the dinner party circuit.
  (TRACK)      
 C2 [ C ]环行物;(尤指)环形道路(或路线、赛道) 
something shaped approximately like a circle, especially a route, path, or sports track that starts and ends in the same place
  They test the car tyres on a motor racing circuit. 他们在环形赛车道上测试轮胎。 
 We made a leisurely circuit of the city walls. 我们悠闲地围着城墙转悠。 
   (CLOSED SYSTEM)      
C2 [ C ](电流的)电路;(液体的)回路 
a closed system of wires or pipes through which electricity or liquid can flow
  A defect was found in the water-cooling/electrical circuit. 在水冷回路/电路中发现了一点毛病。