A turntable is the circular horizontal rotating platform of a phonograph or record player on which the record is placed. If it works properly, it rotates uniformly (evenly). This ensures that the recorded track is played back appropriately. If the turntable is broken then its rotation speed is not constant: sometimes it is faster, sometimes it is slower than it should be. The music is then played back with considerable distortion: when it rotates more slowly, notes are elongated and the pitch is lower; when it rotates more quickly, they are shorter and higher pitched. This kind of distortion can be quite easily recognized.

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Note added at 1 hr (2009-05-31 14:11:00 GMT) Post-grading
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To Tony's remark: let's do the math.
Record players usually operate at 33 turns per minute - that is, one turn takes about 2 seconds. How many notes can you here in one turn? Let's say 20 -- it is probably an OK ballpark figure; higher numbers are not uncommon (in a guitar solo, say).
If the rotation of the record player is just 10% faster in the first half and 10% slower in the second half of each turn, the difference is a whole note at midturn. The rhythm is then completely lost. Likewise, if the music is mixed from various tracks, and the guitar track lags a note behind the drum then I don't see any reason why "extreme delay" would not be appropriate.

If the stylus jumps from one groove then it is usually the record that is broken, not the turntable.