wolf

wolf in figurative and allusive use, the wolf is often taken as the type of savagery and rapacity, explicitly or implicitly contrasted with the meek and vulnerable sheep. From the mid 19th century, the term has also been used as an informal designation of a sexually aggressive male.

A wolf is the emblem of St Edmund the Martyr, St Francis of Assisi, and (as a play on his name) the 10th-century Swabian bishop St Wolfgang.
cry wolf call for help when it is not needed, with the effect that one is not believed when one really does need help, with allusion to the fable of the shepherd boy who deluded people with false cries of ‘Wolf!’; when he was actually attacked and killed, his genuine appeals for help were ignored.
have a wolf by the ears be in a precarious position; the expression is of classical origin, and means that the present situation can neither be maintained nor safely ended.
keep the wolf from the door have enough money to avert hunger or starvation; the wolf here is a type of something that will devour and destroy, as hunger or famine.
wolf in sheep's clothing a person or thing that appears friendly or harmless but is really hostile; often with biblical allusion to Matthew 7:15, ‘Beware of false prophets, which come to you in sheep's clothing, but inwardly they are ravening wolves.’
wolf's head an archaic term for an outlaw, from cry wolf's head, in Anglo-Saxon England uttering a cry for the pursuit of an outlaw as one to be hunted down like a wolf.

See also hunger drives the wolf out of the wood, throw someone to the wolves.