The narrow meaning of idol is an image used as an object of worship. (Literal meaning). But in 2nd Corinthians, Bible through Paul, includes anything that commands ones spiritual allegiance (Figurative meaning).
In the case of the Corinthians, it was whether to eat meat that had been used in a sacrifice to another 'god'.
In Jewish law (not necessarily meaning the Old law, but its interpretation by ancient rabbis), if one does anything that enables or causes anyone else to violate what IS the Old Law then the enabler shares in the guilt of the offender. Thus, if one eats meat that was used in sacrifice, he participates in that sacrifice and violates the having no God before Him commandment.
But Paul explains in 2nd Corinthians many things about this:
First, since we know that idols and the gods to which they are dedicated are meaningless, eating meat or not eating meat reguardless of whether it was previously used in sacrifice is permissable provided:
> That you (the eater) understand that there is no god in the idol.
and
> That those who see you or are otherwise aware of your eating do not misunderstand and connect you and your inner self with that god and thus is not judging the body of Christ.
The sum of this is in 2 Corinthians 10:31-32.
So a literal rendering of Idol is limited to statues or other representations (to us non-existant) gods, a figurative use of the word includes anything that takes HIS place.
A related but distinct issue came in later years over religious icons, which, among other issues resulted in a separation between the Western church and the Eastern Orthodox church.