tailback

1. (UK, Ireland, Commonwealth) A line of motor vehicles causing or the result of traffic congestion or a traffic jam.Examples: "The idea of a British warship supposedly menacing Spain is ludicrous. Is it meant to bomb Cadiz? Will its guns lift a rush-hour tailback in a colony that most Britons regard as awash with tax dodgers, drug dealers and right-wing whingers? The Gibraltarians have rights, but why British taxpayers should send warships to enforce them, even if just "on exercise", is a mystery."Synonyms: backupCommonwealthIrelandUK

2. (American football) A running back or halfback who lines up furthest to the rear in an I formation.