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To talk, explain, expatiate: Go hang around a mouse potato and see if you can get him to geek out and do a brain dump
[1990s+ Computer; based on screen dump, a computer command to print everything appearing on the monitor screen]
(The act of telling someone) everything one knows about a particular topic. Typically used when someone is going to let a new party maintain a piece of code. Conceptually analogous to an operating system core dump in that it saves a lot of useful state before an exit. "You'll have to give me a brain dump on FOOBAR before you start your new job at HackerCorp." At Sun, this is also known as "TOI" (transfer of information).