'Idol' in the Bible

Concerning the eating then of the things sacrificed to idols, we have known that an idol is nothing in the world, and that there is no other God except one;

but not in all men is the knowledge, and certain with conscience of the idol, till now, as a thing sacrificed to an idol do eat it, and their conscience, being weak, is defiled.

what then do I say? that an idol is anything? or that a sacrifice offered to an idol is anything? --

and if any one may say to you, 'This is a thing sacrificed to an idol,' -- do not eat, because of that one who shewed it, and of the conscience, for the Lord's is the earth and its fulness: