Over The Counter :

This is a term for any market where buying and selling is not conducted over an exchange. In this form of trading, transactions are usually executed by telephone.

over the counter :

A decentralized market (as opposed to an exchange market) where geographically dispersed dealers are linked by telephones and computer screens. The market is for securities not listed on a stock or bond exchange. The NASDAQ market is an OTC marketfor US stocks. Antithesis of listed.