(adv.) having no end, limit, or conclusion; boundless; infinite; interminable; incessant
She met him late one night in the winter and watched the stars with him. He told her he loved her two winters later. Three days later, he was sent off to fight in the second World War, leaving her with a promise that she would hold on to for the rest of her life: "And, no matter what happens to me out there, just remember that I will love you endlessly, even if I don't make it home to you."