lack of religion; irreligion; atheism
Refers to the state of having no religious belief or affiliation. Can be used as a noun or adjectival noun.
He is irreligious, but a moral person.
Even irreligious people sometimes participate in religious ceremonies.
無宗教 is a more common term for 'non-religious' or 'having no religion', often used in surveys. 無信仰 can carry a slightly stronger nuance of lacking faith or belief.
Compound of 無 (mu, 'without') and 信仰 (shinkō, 'religious faith').