Closure definition: the act of closing; the state of being closed.. See examples of CLOSURE used in a sentence. From Longman Business Dictionary clo ‧ sure /ˈkləʊʒəˈkloʊʒər/ noun [countable] the act of closing a factory, store, organization etc permanently The factory faces closure if no more money can be found. The company’s 50 high street stores are currently threatened with closure . But I honestly like the Closure + Closure ::fromCallable approach, because string or array as callable has always been weird. Will B. Over a year ago @RoboRobok one reason for requiring only Closure (anonymous function) as opposed to callable, would be to prevent access beyond the scope of the called function. CLOSURE definition: 1. the fact of a business, organization, etc. stopping operating: 2. a process for ending a debate…. Learn more.