substitute teacher
noun🔊/ˌsʌbstɪtjuːt ˈtiːtʃə(r)/
🔊/ˌsʌbstɪtuːt ˈtiːtʃər/
(also informal sub)
(both North American English) (British English supply teacher)
a teacher employed to do the work of another teacher who is away because of illness, etc. 代课教师