DNS cache poisoning is a process by which DNS server records are illegitimately modified to replace a website address with a different address. DNS cache poisoning is used by hackers and crackers to redirect visitors of a particular website to their defined/desired website.
DNS cache poisoning is also known as DNS spoofing.
Techopedia explains DNS Cache Poisoning
DNS cache poisoning works when the security controls of a DNS server are compromised and accessed by a hacker. The hacker replaces a website’s associated DNS records with a different website, one that may contain spam, malware and/or viruses. This is done by changing the associated domain name’s IP address to that of the malicious website. When the user accesses the target website from the corrupted DNS server, the hacker's website appears as opposed to the original website.