Speciesism is to species as racism and sexism are respectively to race and to sex: the will not to give no consideration (or to give less consideration) to the interests of certain individuals to the benefit of others, while putting forward as a justification differences that may be real or imaginary but are always deprived of a logical link to what they purport to justify.
In practice, speciesism is the ideology that justifies and imposes the exploitation and use of animals by humans in ways that would not be accepted if the victims were human.
Animals are raised and slaughtered to furnish us with meat; they are fished for our consumption; they are used as biological models for our scientific interests; they are hunted as a game.
The struggle against these practices and against the ideology that supports them is the task taken up by the animal liberation movement.