Difficult ...unless it sprouts..
More clues would be good - like: you placed an order for xyz - which one might this be? Or - you've been given a boxload of stuff from someone who grows Nerines and Hippeastrums and Hymenocallis and other oddities. Or - you are recent to your garden and there's this ginormous clump...might it be something like Crinum? And then we could, maybe, help a bit. :-))