Real Dictionary

cold call
countable noun: If someone makes a cold call, they phone or visit someone they have never contacted, without making an appointment, in order to try and sell something.

cold call in American English
a telephone call or visit made to a prospective customer without a referral, information sent in advance, etc.
noun: a visit or telephone call to a prospective customer without an appointment or a previous introduction

cold call in British English
noun: a call made by a salesperson on a potential customer without making an appointment
verb: to call on (a potential customer) without making an appointment