| noun | an accumulation caused by clogging or a stoppage “a traffic backup on the main street” |
| noun | someone who takes the place of another (as when things get dangerous or difficult) “the star had a stand-in for dangerous scenes” |
| noun | a musical part (vocal or instrumental) that supports or provides background for other musical parts |
| noun | (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” |
| noun | the act of providing approval and support “his vigorous backing of the conservatives got him in trouble with progressives” |
| back up | verb | become or cause to become obstructed |
| stand in | verb | be a substitute |
| substitute | adjective | serving or used in place of another |
| substitute | verb | act as a substitute |
| relieve | verb | free someone temporarily from his or her obligations |
| fill in | verb | be a substitute |
| accompany | verb | perform an accompaniment to |
| support | verb | play a subordinate role to (another performer) |
| back | verb | give support or one's approval to |