Characteristic of or belonging to the time or state before the fall of man.
Most dictionaries specify that this refers to the Fall of man - the Fall of Adam and Eve - and historically this is a theological term.
But, being a heathen, I am more familiar with it in reference to the prelapsarian sense of peace and harmony implied in Tolkein's works,
or the restoration of prelapsarian, neo-Luddite grace assumed in some post-apocalyptic fantasies,
or the prelapsarian harmony associated with raising all one's own food (a laudable but operose goal).
Etymology: 1800s, Latin, from pre- (before) + lapsus (slip, fall, fall into error; same root as 'lapse') + -ian (pertaining to)