ə.ˈkʌm.pə.ni.mənt ˈbæk.ɪŋ(ɡ) ˈbækˌʌp ˈtʃæmpi.ənʃɪp ˈpeɪtɹənɪd͡ʒ ˈsʌbstɪtʃuːt ˈsʌbstɪtut the act of providing approval and support his vigorous backing of the conservatives got him in trouble with progressives (computer science) a copy of a file or directory on a separate storage device he made a backup in case the original was accidentally damaged or erased a musical part (vocal or instrumental) that supports or provides background for other musical parts someone who takes the place of another (as when things get dangerous or difficult) the star had a stand-in for dangerous scenes we need extra employees for summer fill-ins an accumulation caused by clogging or a stoppage a traffic backup on the main street he discovered a backup in the toilet