A process that relates to endowing objects or locations (wide area of effect) in the environment, with a spell or more permanent Æther fluctuation.
Infused objects or areas often come with some kind of “trigger”. Once the trigger condition is met, the spell that was pre-cast (sequenced) before hand is then executed. Think of traditional “hexes” or “cursed items”. In this way, magi can lay booby traps with spells cast a much earlier time.
Analogy
You could almost think of infusion like an event listener from events in various programming languages. When a specific event is registered, a certain action takes place in response.
The ability to initiate the trigger on an infusion is different from a surrogate mage activating a spell or acting as a conduit. There are a multitude of conditions that can serve as a trigger for infused spells but for surrogates, it the condition is primarily that they are a mage and can “will” the spell out of said object.