Any file to which data is spooled to await the next stage of processing. Especially used in circumstances where spooling the data copes with a mismatch between speeds in two devices or pieces of software. For example, when you send mail under Unix, it's typically copied to a spool file to await a transport demon's attentions.
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Nearby terms: Spool « spool « spooler « spool file » SpoolView » spray » spreadsheet