Definition
Disposable number
A temporary phone number, usually VoIP, issued to receive a single verification code and then discarded.
Disposable numbers power "receive-SMS-online" services and are a staple of OTP-bypass and fake-account fraud. They typically have no stable history and get reused across many unrelated accounts.
Flagging them at signup — via provider association, recency, and reuse — is one of the highest-leverage fraud controls available.