To attach something (frequently something unwelcome and done maliciously) to something desirable.
Commonly used in politics when an unwelcome amendment is added to a bill.
First aide: "You're trying to propulgate a tax bill onto an appropriations package. If we start allowing that, we're never going to get budgets passed."
Second aide: "Would you support a tax cut if it were separate from the budget?"
Third aide: "We're not going to support it while it's attached to the appropriations bill."