1. occurring or done immediately, without any delay; at the same instant
The light turned on instantaneously when I flipped the switch.
A luz acendeu instantaneamente quando liguei o interruptor.
2. in physics, at the same moment in time across all locations (theoretical)
In classical mechanics, forces were thought to act instantaneously.
Na mecânica clássica, as forças eram consideradas como atuando instantaneamente.