to attack someone with a lot of force because they are attacking you with force.

In the face of stiff competition from rival firms we had to fight fire with fire and slash our prices.

• the woman on the street
• the wooden spoon
• the works
• the world and his wife
• the world is oyster
• the world is your oyster
• the worm has turned.
• the worse for wear
• the worst-case scenario
• the worst of both worlds
• the writing is on the wall
• the writing on the wall
• the wrong side of the tracks
• They broke the mould when they made someone.
• They broke the mould when they made something.
• They can whistle for it!
• thick skin
• thick-skinned
• thin end of the wedge
• thing is
• thing of the past
• thing or two
• things have come reached a pretty pass
• things have come to a pretty pass
• think again