As much as one person can think about or hold in mind at one time.
A heartful of desire, man's natural load, A brainful of belief, the noble's lot,—1868, Robert Browning, The Ring and the Book, volume 2 (verse novel), Count Guido Franceschini, page 81, line 179; republished as The Poetical Works of Robert Browning: Volume VIII. The Ring and the Book, Clarendon Press, 2001, →ISBN, page 16:
My only hope is that the memory of my real friendship for each one will blot out the recollection of the brainfuls of non-essentials which they were bidden to bear about with them, at least till the day of reckoning.1924, Elementary English - Volumes 1-2, page 249:
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The truly literate person knows thousands of words, often in several different languages, and has absorbed from listening and reading and seeing (for example, on TV) a whole brainful of thoughts and facts that he can recall and think about.1957, Traffic World:
I can only usefully hold one brainful of detail at a time, and a thousand-line method contains way more than one brainful.2007, Kent Beck, Implementation Patterns:
His Philosophy in Exile course was a brainful. It kicked my ass, but unlike many of my classes, it didn't waste my time.2014, John Vorhaus, Poole's Paradise:
brainful
adj
Etymology From brain + -ful.
1
Characterized by brain activity; cerebral.
Stephens dubbed him, the Peter the Hermit of the tragic secession that drove to a head the great civil revolution, were of the brainful and dominant Scotch-Irish blood, and exemplified its traits and powers.1892, Scotch-Irish Society of America, The Scotch-Irish in America:
For it must ever be that the unconscious, dutiful, studious man, who ever strives to constantly replenish his mind through study, who follows sincerely the true function of his vocation , has within him the brainful power of obtaining the truest element of future reward.1897, The Railway Surgeon - Volume 3, page 12:
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I happen to have met Mr. Carrados in the past and knowing how clever a gentleman he is I took the precaution of cutting the wires as soon as I guessed that he was likely to be busy. Always best with a gentleman so brainful.1934, Ernest Bramah, The Bravo of London:
We are “brainful” until we realize it. Then we can become mindful, at least momentarily, because our frame of reference is now larger.2015, Joseph Emet, Mindfulness Meditation:
Fuck's sake. All this brainful red-pilling and you just trying to throw me off the trail again.2018, Gautam Malkani, Distortion: