What is the definition of a party whip?

As a government bill, C-38 represented the official position of Paul Martin's Liberal government, and the cabinet were thus bound to vote in its favor. Liberal backbenchers and members of the Conservative Party and Bloc Québécois had a free vote. In accordance with its party policy on LGBT rights, the New Democratic Party (NDP) whipped its members in favour. Bev Desjarlais opposed and suffered the withdrawal of her party nomination, and subsequently chose to sit independently during the next session of Parliament. Conservatives tended to vote against the Act, while Bloquistes tended to vote in favour. At least two cabinet ministers stepped down to vote against the bill. Joe Comuzzi resigned just hours before the final vote on the Act, and Martin lamented his leave. As expected, Comuzzi voted against the Act.