Green’s Dictionary of Slang

1. anything that requires no intellectual effort.

1977		B.C. Michael By Alia’s Blood 195: Listen, big guy, if the wind holds out of the east, this should be a no-brainer.
1988		letter in J. Algeo Fifty Years Among the New Words (1991) 241: On two occasions, last year, I overheard students referring to a certain course as being a ‘no-brainer’.
1997–2000		College Sl. Research Project (Cal. State Poly. Uni., Pomona) 🌐 No brainer (adj.) Easy; not much work; little thinking required.
2009		L. McIlvanney All the Colours 116: He asked a few no-brainers.
2010		L. Berney Gutshot Straight [ebook] She didn’t understand his ambivalence [...] This deal was a total no-brainer.

2. an easy decision.

1980		(US) TV Guide 13 Dec. 43: We talk all day long about what the lead should be. Sometimes the decision is a real no-brainer.
1987		Atlanta Constitution 21 Sept. A-14/2: When a major developer looks at the difference between the $400,000 a month a big tenant leasing 20,000 square feet of office space pays, versus the $1,500 a month a gay bar pays in rent, ‘the business decision in that is what we call a no-brainer,’ said the business man.
2002		J. Franzen Corrections 217: It’s a no-brainer. We should all be there. It is so obvious.
2010		Sun. Times Ingear 19 Dec. 9/3: It was a no-brainer.
2015		P. Beatty Sellout (2016) 61: ‘Shit, ostrich meat is indeed the future!’ It sounds like a financial no-brainer.
2015		N. Cummins Tales of the Honey Badger [ebook] It was a no-brainer — we’d stay up high in the fortress.
2016		V. McDermid Out of Bounds (2017) 247: ‘I can see that, Shirley [...] it’s a no-brainer’.
2021		C. Hammer Opal Country 235: ‘Here’s a tip: invest in rare earths. It’s a no-brainer’.

3. a foolish person or thing.

1979		T. Alibrandi Killshot 69: I’ll unanimously be voted the no-brainer-of-the-month award.
1987		Atlanta Journal/Constitution 25 Oct. C-1: If a no-brainer wants to talk on the radio – even if the message makes no sense whatsoever – he or she can do it.

4. attrib. use of sense 1.

1999		Indep. Rev. 27 July 4: No-brainer beefcake roles where brawn beats thesping skills.
2000		Guardian Guide 13–19 May 30: There is no simple way to gauge whether something is unsignable or no-brainer hit material.