In physics and the philosophy of science, instant refers to an infinitesimal interval in time, whose passage is instantaneous. In ordinary speech, an instant has been defined as "a point or very short space of time," a notion deriving from its etymological source, the Latin verb instare, from in- + stare ('to stand'), meaning 'to stand upon or ...
in•stant (ˈɪn stənt) n. 1. an infinitesimal or very short space of time; moment. 2. the point of time now present: Come here this instant! 3. a particular moment: at the instant of contact. 4. an instant beverage or other product, esp. instant coffee.