To do something or perform some task with tremendous fervor, determination, energy, or forcefulness. An allusion to the force with which a blacksmith strikes metal using his or her hammer and tongs. What started as a minor disagreement has escalated into a heated argument, and the two have been at it hammer and tongs ever since.
to do something, especially to argue, with a lot of energy or violence You should have heard last night's argument - they were at it hammer and tongs till four o'clock this morning.