The Collaborative International Dictionary of English v.0.48:

telemarketing \telemarketing\ n.
   the use of the telephone as an interactive medium for
   promotion; calling potential customers by telephone for the
   purpose of selling something; -- applied especially to calls
   made to persons who have not previously contacted the seller.

   Syn: teleselling.
        [WordNet 1.5 +PJC]

WordNet (r) 3.0 (2006):

telemarketing
    n 1: the use of the telephone as an interactive medium for
         promotion and sales [syn: telemarketing, teleselling,
         telecommerce]