A device used to record voice memos
for later playback. More or less the verbal
equivalent of a notepad.
These devices range from portable handheld devices with small audio casettes (much like those you sometimes see reporters or writers using in movies) to desktop models used to record lengthy letters and documents for later typing - eg: "Jane, take a letter".
The higher end models have refinements such as voice activation and electronic storage removing the need for tapes, along with other bells and whistles to make talking to yourself just that bit more fun.
Which reminds me of a joke I heard the other day.
Tim: "Hey Steve, can I use your dictaphone?"
Steve: "No, use your finger like everyone else!"