Oh dear. That sounds like an ex-lilac tree, as they're coming into flower now. Try sraping a littl piece of bark off to see what colour the wood is underneath - if it's brown, it's dead. Are there any signs of life at all? No new shoots? Sorry, guest. :-(((((

If you cut out all the dead branches it may re-sprout from lower down if the roots are still alive. Lilacs sucker anyway so this could well happen. I lost an Autumn flowering cherry this winter, so I commiserate with you!