1. occurring or done immediately, without any delay; at the same instant

Examples

• The light bulb turned on instantaneously when I flipped the switch.
• She responded instantaneously to the emergency call.
• The chemical reaction occurred instantaneously when the two liquids mixed.
• The news spread instantaneously across social media.
• The pain disappeared instantaneously after taking the medication.
• He understood the problem instantaneously without needing an explanation.