A groove on a record that is, well, locked. Normally, vinyl records are pressed in a spiral so that it proceeds normally. However, sometimes, a spiteful musician, or one who thinks he or she is being funny will lock a groove so the same thing keeps repeating over and over and over...

The only time I've seen this pulled off successfully (i.e. it took a person a while to realize something was wrong) was on the Sonic Youth LP EVOL, the song being Expressway To Yr. Skull.