The Collaborative International Dictionary of English v.0.48:

Prolation \Pro*la"tion\, n. [L. prolatio: cf. F. prolation.]
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   1. The act of prolating or pronouncing; utterance;
      pronunciation. [Obs.] --Ray.
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   2. The act of deferring; delay. [Obs.] --Ainsworth.
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   3. (Mus.) A medi[ae]val method of determining of the
      proportionate duration of semibreves and minims. --Busby.
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