- in|stant1 S3 [ˈınstənt] adj[Date: 1400-1500; : French; Origin: Latin instans, present participle of instare 'to stand on, be present', from stare 'to stand']1.) [usually before noun]happening or produced immediately= ↑immediate▪ an instant success▪ a system that provides instant access to client information▪ The women took an instant dislike to one another.▪ The programme brought an instant response.2.) [only before noun]instant food, coffee etc is in the form of powder and prepared by adding hot water▪ instant coffee▪ instant soupinstant 2instant2 n1.) [usually singular]a moment▪ She caught his eye for an instant .▪ When the rain started, the crowd vanished in an instant (=immediately) .instant of▪ an instant of panic▪ She stepped towards the door and in that very same instant, the doorbell rang.2.) the instant (that)as soon as something happens▪ The instant I saw him, I knew he was the man from the restaurant.▪ Jen burst out laughing the instant she walked in.3.) this instantspoken used when telling someone, especially a child, to do something immediately= ↑now▪ Come here this instant!
Dictionary of contemporary English. 2013.