truthy

From truth +‎ -y. In colloquial sense, back-formation from truthiness.

• (UK) IPA^(key): /ˈtɹuːθi/
• Rhymes: -uːθi

truthy (comparative truthier, superlative truthiest)

1. (obsolete or humorous) Faithful; true. [19th c.]

   Synonyms: faithful, honest

   • c. 1800, J. H. Colls, Theodore:

     You […] are afraid Theodore your sweetheart shouldn't prove truthy.

   • 2016 June 3, Seija Rankin, “It's National Doughnut Day, so Let's Relive the Best Doughnut Moments in Pop Culture”, in E! Online‎:

     Mindy Lahiri is never one to mince words, and most of the things that come out of her mouth are rife for a gospel. But her sheer overwhelming emotion at her doughnut craving is one of the truthiest truthisms she's ever truthed. Preach, girl.

2. (US, colloquial) Only superficially true; that is asserted or felt instinctively to be true, with no recourse to facts. [from 21st c.]

   Synonyms: truthlike, truthful, truthsome, veridical

   • 2011, Steven Pinker, The Better Angels of Our Nature, Penguin, published 2012, page 595:

     Historians today point out that each of these ringing assertions was, at best, truthy.

3. (programming) Evaluating to true in a Boolean context.

   Antonym: falsy

   • 2012, David Flanagan, JavaScript Pocket Reference, page 40:

     In JavaScript, any expression or statement that expects a boolean value will work with a truthy or falsy value, so the fact that && does not always evaluate to true or false does not cause practical problems.

   • 2013, Dan Wellman, jQuery Hotshot, →ISBN:

     In JavaScript, as well as the true or false Boolean values, other types of variables can be said to be truthy or falsey.

   • 2014, Eric T. Freeman, Elisabeth Robson, Head First JavaScript Programming: A Brain-Friendly Guide, →ISBN, page 292:

     To remember which values are truthy and which are falsey, just memorize the five falsey values - undefined, null, 0, "" and NaN -- and remember that everything else is truthy.

   • 2015, Daniel Higginbotham, Clojure for the Brave and True, →ISBN, page 40:

     Clojure uses the Boolean operators or and and. or returns either the first truthy value or the last value, and returns the first falsey value or, if no values are falsey, the last truthy value.

• truthiness

• facty

• Oxford English Dictionary, 1884–1928, and First Supplement, 1933.