The Jargon File (version 4.4.7, 29 Dec 2003):

braino
 /bray'no/, n.

    Syn. for thinko. See also brain fart.


The Free On-line Dictionary of Computing (30 December 2018):

thinko
braino

    /thing'koh/ (Or "braino", by analogy with "typo") A
   momentary, correctable glitch in mental processing,
   especially one involving recall of information learned by
   rote; a bubble in the stream of consciousness.

   See also brain fart.  Compare mouso.

   [Jargon File]

   (1996-04-20)